Characteristics of Epstein-Barr virus activation of human B lymphocytes.

Epstein-Barr virus (EBV) will infect at least every third cell if exposed in vitro to an extensively purified B cell population from human peripheral blood. About 10% of such infected cells will be driven into immunoglobulin synthesis and secretion, as judged by the indirect protein A plaque assay. The appearance of EB nuclear antigen, de novo DNA synthesis, and immunoglobulin secretion are linked phenomena accompanying infection as judged by viral dilution experiments, which yield kinetics of a one-hit order. Induction of immunoglobulin secretion in B cells by EBV requires de novo synthesis of DNA, and consequently, nontransforming EBV (P3HR1) will not induce immunoglobulin secretion and will also specifically block such induction from subsequently added EBV. The termination of immunoglobulin induction by EBV in short-term cultures appears to be T cell dependent.

Anonymous HIV surveillance with risk factor elicitation at Scotland's largest prison, Barlinnie.

OBJECTIVE: To determine prevalence of HIV infection and risk behaviours among male inmates of Her Majesty's Prison (HMP) Barlinnie, Glasgow, Scotland on 8-9 September 1994. DESIGN: Cross-sectional study: voluntary, anonymous HIV surveillance (using saliva samples) of all inmates and linked self-completion risk-factor questionnaire. SUBJECTS: Of 1073 prisoners available to participate, 985 (92%) completed a risk-factor questionnaire and 982 salivettes were received for testing, of which 978 were tested for HIV antibodies (four were dry samples); 928 questionnaires passed logical checks for consistency. MAIN OUTCOME MEASURES: HIV prevalence on saliva testing, related risk behaviours and ratio of overall-to-disclosed HIV prevalence. Proportion of all inmates who have ever injected drugs, ever injected inside prison, started injecting inside, ever had acute hepatitis, had a recent personal HIV test (since January 1993). RESULTS: Nine saliva samples [eight injecting drug users (IDU), one recognized other risk] out of 978 were HIV-antibody-positive (three presumptively from known HIV-infected inmates). Overall HIV prevalence was estimated at 1% compared with a known prevalence of 0.4%, giving an overall-to-disclosed HIV prevalence ratio of 2.6 in HMP Barlinnie in September 1994. A higher proportion of prisoners from Glasgow (48%) than elsewhere (19%) were IDU. Year of first injection was also different by residence with 23% of Glasgow IDU having first injected after 1988 compared with 45% of IDU from elsewhere, mainly West and South Scotland. Half the IDU inmates reported having injected while incarcerated and 6% had started to inject while incarcerated. Ten per cent of all prisoners and 20% of IDU inmates had had a personal HIV test since January 1993. Logistic regression showed that there was a significant deficit of recent HIV test uptake by Glasgow residents (odds ratio, 0.5; 95% confidence interval, 0.27-0.89), that IDU were more likely to have had treatment for a sexually transmitted disease, and that IDU who had injected inside and those whose injecting career began prior to 1989 were more likely to have had acute hepatitis. CONCLUSION: A consistent harm-reduction policy is needed across prisons in the United Kingdom to avoid transmission of blood-borne viral infections. Drug injecting inside prison is common, a proportion of IDU inmates having first injected drugs while in prison, and much higher rates of hepatitis have been reported in association with injecting while incarcerated compared with that for IDU who only injected outside prison.

Anonymous HIV surveillance in Saughton Prison, Edinburgh.

OBJECTIVES: To estimate the prevalence of HIV by anonymous saliva testing in Her Majesty's Prison, Saughton (Saughton Prison), Edinburgh, UK. To elicit linked anonymous risk factor information from which to estimate risk scores for those who had taken an HIV blood test and, among drug injectors, for those who were HIV-1-antibody-positive on saliva testing. SETTING: Saughton Prison on 15 and 16 August 1991; HIV Immunology and Regional Virus Laboratories, Edinburgh, and the Medical Research Council Biostatistics Unit, Cambridge, UK. PARTICIPANTS: Male inmates (378 out of a total of 499) of Saughton Prison. MAIN OUTCOME MEASURES: Answers to a brief questionnaire about age, usual residence, present and past custodial sentences, drug injecting and sexual behaviour prior to and in prison, HIV testing and history of acute hepatitis. HIV-1-antibody status was established by saliva testing. RESULTS: Eighteen per cent of participants were injecting drug users (IDU), of whom approximately one-half (47%) had injected while inside prison. Ninety men (26%), including 40 (14%) of 278 participants who had never injected drugs and 77% of IDU participants, had taken an HIV blood test. Nine per cent of all participants and 35% of IDU participants had had an acute attack of hepatitis. Forty-one (62%) of 66 IDU had been imprisoned five or more times before their current prison sentence. After taking account of region of residence, injecting drug history and acute hepatitis, aspects of sentencing and sexual behaviour were not determinants of those who had been tested for HIV. On the study days, 18 out of 499 (3.6%) participants were known to prison medical officers to be HIV-infected. Following saliva testing, HIV prevalence was 17 out of 375 (4.5%) inmates tested. All 17 had at some time 'taken the blood test for HIV' and all had injected non-medically prescribed drugs. Edinburgh residence, age 26-30 years, have injected in prison and having first injected before 1983 all contributed to the risk score for whether an IDU was HIV-1-antibody-positive on saliva testing. CONCLUSIONS: Documented HIV prevalence in saliva was 4.5%, which--assuming no volunteer bias (as supported by questionnaire returns)--suggests that actual HIV prevalence was 25% greater than revealed to Saughton's prison medical service. All 17 inmates who were HIV-1-antibody-positive on saliva testing had injected non-medically prescribed drugs. The high reported frequency by inmates of injecting in prison highlights the urgent requirement for drug reduction and rehabilitation programmes for injecting inmates. Linked anonymous voluntary HIV testing of saliva can provide valuable information about HIV prevalence for the planning of prison resources and policy.

Beta 2-microglobulin levels in drug users: the influence of risk behaviour.

beta 2-microglobulin (beta 2M) levels were measured in 217 Edinburgh drug users to assess their usefulness as a marker for HIV-related disease. Eighty HIV-seronegative drug injectors had significantly higher levels than 100 HIV-seronegative blood-donor controls. Amongst 137 asymptomatic HIV-seropositive drug users, those who were defined as continued drug users had significantly higher beta 2M levels and percentages of CD3+ T lymphocytes with DR Class II expression than non-injecting drug users. beta 2M levels correlated with the percentage of activated DR+ CD3+ T lymphocytes. These findings indicate that changes in beta 2M levels may reflect differences in drug-injecting behaviour and are not influenced solely by HIV status or progression. These changes in beta 2M probably represent differing degrees of immunostimulation resulting from the antigenic challenges afforded by continued or frequent drug injection. It is important to establish normal ranges for beta 2M from HIV-seronegative controls who are matched with respect to risk group and behaviour. All these factors should be taken into account if beta 2M is to be used as a marker of HIV progression.

Clinical and epidemiological implications of the Centers for Disease Control/World Health Organization reclassification of AIDS cases.

OBJECTIVE: To establish whether various accepted and proposed AIDS definitions have clinical and biological validity: because the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) reclassifications of AIDS are important not only for describing the epidemiology of HIV disease but also to individual patients. SETTING: Regional Infectious Diseases Unit, City Hospital, Edinburgh, Scotland, UK. PATIENTS: We analysed the disease progression of 532 HIV-seropositive individuals seen at the City Hospital, Edinburgh, up to the end of July 1991. MAIN OUTCOME MEASURES: Annual numbers of potentially reportable cases from the Edinburgh City Hospital Cohort according to three proposed AIDS case definitions based on: (1) first lymphocyte count < or = 1000 x 10(6)/l; (2) first CD4 cell count < or = 200 x 10(6)/l; or (3) first of two consecutive CD4 cell counts < or = 200 x 10(6)/l. Lifetables to death (irrespective of cause) from month of satisfying the above case definitions, and proportion of patients who satisfied each definition in their calendar year of enrollment in the cohort are reported. RESULTS: There is a threefold increase in patients in the Edinburgh City Hospital Cohort defined as having AIDS under the 1987 and the proposed 1992 CDC definitions--a substantial change for patients and epidemiologists alike. That they are describing different immunodeficiency states is clear from lifetable analysis, which reveals median survivals of 20 and 50 months under the 1987 and the proposed 1992 AIDS definitions, respectively. For epidemiological purposes, redefinitions based on the WHO proposed classification of HIV disease using either a lymphocyte count < or = 1000 x 10(6)/l or a CD4 cell count < or = 200 x 10(6)/l are broadly interchangeable. They are not equally effective for monitoring individual progression (CD4 cell count is superior). Both, for different reasons, lack biological plausibility. CONCLUSIONS: We therefore suggest that the stricter, biologically more plausible, case definition used in Scotland of two consecutive CD4 cell counts of < or = 200 x 10(6)/l [CD4(200) (x 2)] should be adopted--not as a new definition of AIDS, but as an additional important state of severe HIV-related immunodeficiency (SHRID). Median survival under the CD4(200) (x 2) case definition was 40 months in the Edinburgh cohort. We have illustrated differences in CD4(200) case ascertainment between injecting drug users and other HIV-infected patients in the Edinburgh City Hospital Cohort. We recommend that surveillance centres should ascertain date of first immunological monitoring as well as date of SHRID diagnosis in order to identify differential case ascertainment.

Progression of HIV: follow-up of Edinburgh injecting drug users with narrow seroconversion intervals in 1983-1985.

OBJECTIVE: To describe progression and survival of individuals infected with HIV by injecting drug use in Edinburgh. DESIGN AND METHODS: From 313 HIV-infected patients with retrospectively estimated narrow seroconversion intervals, 260 infected via injecting drug use in the years 1983-1985 were selected for the study group. MAIN OUTCOME MEASURES: The effects of gender, age, human leukocyte antigen (HLA) type and zidovudine (ZDV) treatment on progression and survival from seroconversion; Weibull estimates of the AIDS incubation distribution and the overall survival distribution; slopes of absolute CD4 lymphocyte loss (on the square root scale) and loss of CD4 percentage. RESULTS: The cumulative progression rates at 10 years were 68% to CDC stage IV and 31% to AIDS with a mortality rate of 25%. Three-year survival rates for AIDS and CDC stage IV cases were 25 and 72%, respectively. Gender and age effects on progression or overall survival were not found, although those aged over 30 years experienced poorer survival from AIDS. A strong HLA (A1, B8, DR3) association with faster progression and poorer survival was found. Median survival was estimated by Weibull distribution to be 12.6 years; median AIDS-free time was estimated to be 11.6 years. CD4 cell loss was approximately linear when transformed to the square root scale as was the decline in CD4 percentage. Only HLA effects on slopes were found: A1,B8, DR3 was significantly associated with faster loss of both absolute CD4 cells and CD4 percentage (P < 0.001) and B27 was significantly associated with slower loss of CD4 percentage (P = 0.01). CONCLUSIONS: Edinburgh IDU do not seem to progress more rapidly than other cohorts with predominantly different risk activities. Older age was associated with poorer survival from AIDS but no gender effect was found for progression or overall survival. The clearest significant association with AIDS progression, mortality and loss of CD4 cells was the phenotype HLA A1,B8,DR3. In contrast HLA B27 was associated with slower loss of CD4 cells.

Increased expression of the CD45RO (memory) antigen on T cells in HIV-infected children.

Expression of the CD45RO putative memory cell antigen on CD4 (helper) and CD8 (cytotoxic/suppressor) lymphocytes of children born to HIV-infected women was investigated using the UCHL1 antibody. Significantly raised numbers of CD45RO+ CD8 lymphocytes were found in all nine of the infected children compared with uninfected and control children. Expression of CD45RO on CD4 lymphocytes was variable; absolute numbers were not increased, although the percentage was increased in four out of nine infected children. All the infected children except two (who had comparatively low numbers of CD45RO+ CD8 cells) were clinically well, which suggests that an increase in CD45RO+ CD8 cells may be indicative of a functionally active immune response against HIV.

HIV infection in women: immunological markers and the influence of pregnancy.

OBJECTIVE: To describe the influence of pregnancy on immunological marker paths and progression of HIV-infected women. DESIGN: Analysis of prospectively collected immunological and clinical data collected on 145 women reviewed at the City Hospital, Edinburgh, between 1985 and 1992 using a two-level random-effects model that allows for within- and between-patient variance. RESULTS: There were differences between the marker paths of women according to risk activity; women who had acquired HIV via injecting drug use (in addition to heterosexual intercourse) had a higher level of absolute CD4 cells, CD4% and total lymphocytes at seroconversion than those who had acquired HIV via heterosexual intercourse alone; however, immunological markers declined more steeply after seroconversion. There was no evidence that pregnancy, either before or after HIV seroconversion had an adverse effect on marker paths of HIV disease. There was a significant association between pregnancy after HIV seroconversion and post-pregnancy changes in immunological markers: an increase in the CD4% and a decrease in CD8%. However, causality cannot be implied as pregnancy itself may be associated with considerable lifestyle changes. During pregnancy the total white blood count rose due to an increase in the number of granulocytes, whereas the total lymphocyte numbers fell. The absolute CD4 lymphocyte subset counts fell progressively but the effect was due to the fall in the total lymphocyte counts, there being no influence of pregnancy on either CD4% or CD8%. CONCLUSIONS: In asymptomatic HIV infection, changes in the absolute levels of CD4 and CD8 lymphocyte counts are primarily related to changes in the other components of the white cell count because there were no changes in CD4% and CD8%. Pregnancy itself has no adverse effect on immunological markers of HIV.

Subclass distribution of IgG autoantibodies in bullous pemphigoid.

The distribution of IgG subclasses in the antibasement membrane zone autoantibody of pemphigoid in skin and serum was analyzed by use of monoclonal antibodies to human IgG subclasses. The predominant subclass was IgG4 which was present in 23 of 24 skin biopsies, IgG1 was next and IgG3 was found only occasionally. In 3 of 24 biopsies IgG4 was the only IgG subclass detected, C3 was absent in 2 of these, the third contained IgM and C3. Serum autoantibodies were similarly analyzed by indirect immunofluorescence (IIF) when again IgG4 autoantibody was the dominant subclass. No IgE autoantibody was detected by IIF.

Addition of polyethylene glycol 6000 improves the sensitivity of the protein A plaque assay for detection of human immunoglobulin secreting cells.

A technical modification of the protein A plaque assay is described in which the addition of polyethylene glycol 6000 results in increased sensitivity in detection of human immunoglobulin secreting cells. Optimal conditions for use of this modification are described which result in improved detection and visualisation of haemolytic zones and have, with continued use, been shown to improve the reproducibility and reliability of this assay.

The separation of human serum IgG into subclass fractions by immunoaffinity chromatography and assessment of specific antibody activity.

Murine monoclonal antibodies ( McAbs ) with specificity for subclass-specific or subclass-restricted determinants on human IgG have been coupled to Sepharose to generate affinity columns. The judicial use of positive and negative chromatography and the exploitation of the special properties of individual McAb affinity columns has allowed the preparation of individual IgG subclasses from polyclonal IgG containing less than 1% contamination by any other IgG subclass. The specificity of the antibodies present in each polyclonal IgG subclass preparation has been assayed against a bacterial toxoid (tetanus), 2 bacterial cell wall antigens (E. coli and pneumococcal) and coat antigen(s) of a DNA virus (CMV). Antibodies were predominantly IgG1 to tetanus toxoid, IgG2 to pneumovax and E. coli cell walls, and IgG1, 2 and 3 to CMV coat antigens.

Enzyme linked immunosorbent assay (ELISA) for the detection of serum antibodies to the inner core lipopolysaccharide of Neisseria meningitidis group B.

We have developed a solid-phase ELISA to study the human immune response to inner core lipopolysaccharide (LPS) of Neisseria meningitidis (Nm) using structurally defined glycolipids from a genetically defined mutant (galE) of a serogroup B Nm strain. Previous studies had demonstrated that a galE (inner core) LPS epitope is conserved in approximately 70% Nm strains and was accessible to antibody in fully encapsulated wild-type Nm strains. A murine monoclonal antibody, MAb B5, raised to a galE mutant of serogroup B Nm strain, immunotype L3 (B.15.P1.7,16) was used to determine the specificity of the inner core LPS ELISA by inhibition studies using purified galE LPS and human sera. The intra-assay coefficient of variation (CV) was 5-6% and inter-assay CV was 19-22%. Using this ELISA, significant differences in the geometric mean titres (GMTs) of naturally occurring serum antibodies (specific to inner core LPS) between healthy adults (18-65 years, N=54) and healthy infants (3-4 months, N=144) of both IgG and IgM classes were found (P<0.0001). GMTs were expressed in galE arbitrary units (AU/ml) (95% confidence intervals): IgG antibodies in adults 5.7 (5. 0,6.9) and in infants 1.1 (1.0,1.3); IgM antibodies in adults 7.7 (5. 7,10.4), and in infants 0.85 (0.7,1.1). In age-matched children aged 26-113 months a difference (P=0.04) in specific IgG was found in healthy infants and infants in the acute phase of invasive Nm disease (GMT (95%CI) in AU/ml: in healthy infants 7.7 (5.3,11.0), in acute phase infants 4.2 (2.5,7.2). However, there was no difference in specific IgM (P=0.98) between these groups healthy infants 4.7 (3. 1,7.0), acute phase 4.6 (2.9, 7.4). In eleven children (5-181 months) there were differences in the GMTs of specific IgG and IgM (P=0.02, P=0.008 respectively) between paired acute and convalescent sera (GMT) (95%CI) in AU/ml: IgG acute 1.95 (0.98, 3.8), convalescent 5.2 (2.2,12.4); IgM acute 1.78 (1.05,3.0), convalescent 4.38 (2.6,7.3). We conclude that ELISA is a specific, sensitive and reproducible method for the detection of antibodies to inner core LPS of Nm and that an epitope defined by MAb B5 can be immunogenic in infants and adults. These findings are relevant to the potential candidacy of inner core LPS as a vaccine.

B cell differentiation and lymphocyte surface phenotype in late onset hypogammaglobulinaemia.

Lymphocyte function and cell surface phenotype were examined in fifteen patients with late onset hypogammaglobulinaemia. The percentage of surface immunoglobulin-positive B cells in fourteen of the fifteen patients was in the normal range. Patients' B cells expressed MHC class II antigens at normal levels. For one patient, there was relatively high sIgD and low sIgM expression on B cells; the rest of the patients did not differ from controls in surface immunoglobulin density. The proportion of B cells positive for CD5 in patients was comparable to normal controls, and considerably less than in cord blood. However, the pattern of immunoglobulin isotype secretion in vitro by patients' B cells closely paralleled responses of cord blood B cells. Spontaneous secretion of IgM and IgG by patients' B cells was very low. Following polyclonal activation in the presence of autologous T cells, cells from thirteen patients secreted IgM within the normal range in response to at least one activator. The response of patients' purified B cells to IL-2 and gamma-IFN was variable. For four of six tested, B cells cultured with IL-2 and gamma-IFN together with polyclonal activators secreted normal levels of IgM. B cells from the other two patients secreted little or no IgM in response to these cytokines. For fourteen patients, IgG secretion following polyclonal activation remained low both when B cells were cultured with T cells or with a combination of IL-2 and gamma-IFN. IgG subclass imbalance was seen in one patient, whose cells secreted an unusually high proportion of IgG3, and undetectable IgG2 and IgG4; this pattern was consistent whether T cell help was provided by autologous or allogeneic T cells. Similarly purified B cells from this patient showed deficient IgG2 and IgG4 production in response to IL-2 and gamma-IFN.

Lymphocyte subpopulations in early human pregnancy.

OBJECTIVE: To examine changes in lymphocyte subpopulations in early pregnancy using a methodologically appropriate study design that addresses previous sources of bias. METHODS: Thirty-seven healthy women without risk factors for human immunodeficiency virus (HIV) were reviewed when less than 9 weeks pregnant (median 51 days, range 44-61) and again at least 4 weeks following termination of pregnancy. No woman took the oral contraceptive pill. Blood was taken on each occasion at the same time of day under the same conditions of rest and food intake, transported immediately to the laboratory, and directly prepared for analysis. Lymphocyte surface markers were determined by staining with dual-colored, isotype-matched monoclonal antibody fluorescent conjugates, followed by whole blood lysis and subsequent flow cytometric analysis. RESULTS: Pregnancy was associated with a significant reduction in total lymphocytes (P < .0001) and also in CD4+ cells, whether expressed as a percentage of lymphocytes (P = .004), an absolute count (P = .0006), or a ratio (P = .01). Change was independent of the basal level except for lymphocytes, and almost all indices had significant correlations between pregnant and nonpregnant values. CONCLUSIONS: In this study design, each woman served as her own control and all factors remained constant except the pregnancy state. Early pregnancy causes a reduction in total lymphocytes of about 6% expressed as a percentage of total white cell count, and in CD4+ cells by 3% as a percentage of lymphocytes, or 100/mm3. We believe this fall can be accepted as definitive.

Study size and documentation to detect injection-related hepatitis C in prison.

We used existing data on hepatitis C prevalence, injection-related hepatitis C transmission and needle use in prisons and new data on infectiousness, to estimate the size of study required to detect injection-related hepatitis C in UK prisons. A pilot study of 500 prisoners followed for 10 weeks would have a 65% chance of detecting a hepatitis C seroconversion, conservatively assuming one injection per prisoner per week, and a 3% transmission rate per injection, but uncertainty might persist as to whether transmission had occurred during a short incarceration or before it. If the actual transmission rate was 10%, as recently documented, then such a study would have more adequate statistical power. A definitive study of 3000 prisoners for 10 weeks would expect to detect about six seroconversions, even with conservative estimates of injection frequency and transmission rate. Adequate design and power of these studies is important because of the complacency that could result from false-negative findings. We suggest six risk-factor themes that studies should document.

The Edinburgh City Hospital cohort: analysis of enrollment, progression and mortality by baseline covariates.

We describe baseline characteristics, enrollment, progression and mortality of the Edinburgh City Hospital HIV cohort. There were 431 men and 191 (31%) women; 439 (71%) infected via injection drug use (IDU); 92 (15%) via homosexual intercourse; 84 (13%) via heterosexual intercourse and 7 from blood products. Median annual rate of CD4 cell loss was 49 (90% range: 15-146); Both homosexual men and patients aged > 40 years at enrollment lost CD4 cells significantly more quickly. In multifactorial analysis controlled for baseline CD4 count and IgA, there was no gender effect, but young patients (< 25 years) progressed significantly more slowly to AIDS (RR 0.4, p = 0.00). Homosexual men progressed significantly more quickly than IDUs, with adjusted relative risks (RR) of 2.9 (p = 0.00), 2.5 (p = 0.01) and 1.5 (p = 0.1) for progression to CDC stage IV, AIDS and death, respectively. The three-year survival rate post-AIDS was 25% (SE 4.3) and there was no gender effect on survival. There was, however, an age effect whereby individuals diagnosed with AIDS in their 40s or later showed poorer survival (RR 1.9, p = 0.04). Zidovudine treatment after an AIDS diagnosis significantly lengthened post-AIDS survival (RR 0.5, p = 0.08).

Prevalence of hepatitis C in prisons: WASH-C surveillance linked to self-reported risk behaviours.

We used cross-sectional willing anonymous salivary hepatitis C (WASH-C) surveillance linked to self-completed risk-factor questionnaires to estimate the prevalence of salivary hepatitis C antibodies (HepCAbS) in five Scottish prisons from 1994 to 1996. Of 2121 available inmates, 1864 (88%) participated and 1532/1864 (82%) stored samples were suitable for testing. Overall 311/1532 (20.3%, prevalence 95% CI 18.3-22.3%) were HepCAbS-positive: 265/536 (49%, 95% CI 45-54%) injector-inmates but only 27/899 (3%, 95% CI 2-4%) non-injector-inmates. Among injectors, HepCAbS positivity was only slightly higher (p = 0.03) in those who had injected inside prison (53%, 162/305) than in those who had not (44%, 98/224). Those who began injecting in 1992-96 were much less likely to be HepCAbS-positive than those who started pre-1992 (31%, 35/114 vs. 55%, 230/422; p < 0.001). Even with injectors who began in 1992-96 but had never injected inside prison, the prevalence of hepatitis C carriage was 17/63 (95% CI 16-38%). The prevalence and potential transmissibility of hepatitis C in injector-inmates are both high. Promoting 'off injecting' before 'off drugs' (both inside and outside prison), methadone prescription during short incarcerations, alternatives to prison, and support of HepCAbS-positive inmates in becoming eligible for treatment, all warrant urgent consideration.

Immunodeficiency in non-tuberculous mycobacterial disease.

T-cell immunity was investigated in eight patients with non-tuberculous mycobacterial disease, to see whether impaired immune function might be the explanation for their infection. Cellular immune function was evaluated in vitro by measuring the proliferation of peripheral blood mononuclear cells in response to both non-specific mitogens (phytohaemagglutinin and pokeweed mitogen) and specific recall antigens (streptokinase-streptodornase and purified protein derivative from Mycobacterium tuberculosis), and in vivo, by measuring the skin test response to a panel of recall antigens. Functionally relevant T-lymphocyte sub-populations (CD4, CD8, activated CD3 and gamma/delta T-cells) were enumerated by two-colour flow cytometry. The results were compared with those for a group of patients with pulmonary tuberculosis, with groups of controls matched for age and smoking habit, and with a patient group receiving steroid treatment. The patients with non-tuberculous mycobacterial disease had poor or absent skin test responses; in vitro, their response to recall antigens was depressed, although their response to mitogens was normal. The patients had significantly raised levels of CD8 lymphocytes and activated T-cells, but lacked any circulating gamma/delta T-cells. There were also differences between the various control groups. In conclusion, this study demonstrates a deficiency in the cellular immune system of these patients, which is most readily detectable by skin testing, or by measuring lymphocyte proliferative responses to recall antigens. However, the study also shows changes in cellular immune responses in controls matched for age and smoking and in patients on steroid treatment, and underscores the need for matched controls. Further work needs to be done to ascertain whether the cellular immune deficiency is a cause of, or is caused by, the mycobacterial infections, and also to investigate the pathological significance of the alterations in T-cell sub-populations.

Occupational risk and precautions related to HIV infection among dentists in the Lothian region of Scotland.

This retrospective study used a postal questionnaire to measure occupational risks and to assess infection control procedures among 310 dental practitioners. The study comprised general dental practices in the Lothian region of Scotland, Lothian Health Board Community Dental Service and Edinburgh Dental Hospital. Altogether, 217 dental practitioners responded by the due date giving recall of inoculation injuries within the previous 5 years and infection control measures employed. The study revealed that 191 practitioners (88%) had completed a course of hepatitis B vaccination but one-third of them had not been tested for post-vaccination antibody. In 1991, two thirds of dentists (66%: 137 of 207 respondents) wore the same pair of gloves, and 80% of dentists (142 of 177 respondents) wore the same mask, for dealing with more than one patient. The usual practice was to change gloves during sessions (44%: out of 71 dentists) and to change masks for each session or less often (75%: 73 out of 97 dentists). The proportion of dentists who never used gloves fell from 56% in 1981 to 1% in 1991. An autoclave was used for sterilisation by 85% of practitioners in 1991. Reported non-sterile inoculation injuries averaged 1.7 (S.D. = 3.2) injuries per dentist in the previous year with 56% of practitioners having had an injury. The average was 6.8 (S.D. = 15.9) injuries per dentist in the previous 5 years with 76% of practitioners having had an injury. Of recent non-sterile inoculation injuries described by dental practitioners, 30% constituted a moderate or high risk of transmission of infection to the practitioner (43 of 141 described injuries). Combined with HIV seroprevalance rates, probabilities of transmission and numbers of practising dentists, the mean reported number of non-sterile inoculation injuries in the previous 5 years may be used to provide estimates of expected numbers of dental practitioners occupationally infected with HIV in the previous 5 years. U.K. estimates were 0.004 dentists in Lothian region and 0.05 dentists in the Thames region occupationally infected with HIV in the previous five years. Non-sterile inoculation injuries appear to be a common hazard of dental practice. In any year, most dentists are exposed to the risk of blood-borne viral infection. Despite a high reported incidence of such injuries, dental practice within the U.K. appears to carry a low risk of acquiring HIV infection from occupational exposure.

Total IgE and allergen-specific IgE assays: guidelines for the provision of a laboratory service.

The Analytical Methods Working Party of the Association of Clinical Biochemists (ACB) established this Task Force to consider the measurement of total serum IgE and specific IgE. The aims were to give general guidance on available methods of assay; to survey commercial kits and 'in-house' methods; to investigate performance based on external Quality Assessment and independent evaluation, and to advise on criteria laboratories should consider before setting up IgE and specific IgE assays.