A stable form of delayed-type hypersensitivity.

An antigen dose below the level needed to provoke an antibody response produces in mice a persistent, but minor degree of delayed-type hypersensitivity (dth) to sheep red blood cells. The DTH is unstable. It is erased by larger doses of antigen and cannot be built upon by further antigenic stimulation. The much higher levels of DTH resulting from immunization under the modulating influence of cyclophosphamide (CY) or BCG persist under strong secondary antigenic stimulation, though the former is subject to partial suppression unless CY is used to prevent the secondary humoral response. The DTH produced by a BCG-modulated primary response is not subject to this suppressive effect of a secondary antibody response. In this case the anamnestic T-cell response is very brisk and cannont be potentiated by giving CY at the time of the secondary antigenic stimulus. This effect is not due to the modulating influence of a residual BCG infection. It results from a permanent change induced during the primary response. The mediator cells formed under the influence of BCG are apparently resistant to inhibition by blocking serum containing immune complexes. Even the actively dividing T cells which are susceptible to vinblastine, and most readily blocked in the absence of BCG, are highly resistant to blocking by immune complexes. It is not clear whether these cells are intrinsically different or whether their insensitivity to blocking results from features peculiar to the humoral response that accompanies a BCG-modulated primary response. The mediator cells produced by both BCG- and CY-modulated responses become vinblastine resistant, relatively insensitive to humoral blocking factors, and capable of surviving in a functionally active form in syngeneic recipients with an apparent half-life of about 50 days. There were indications, however, that their effective life-span may be greatly extended in some circumstances by persisting antigenic stimulation; and in the case of BCG-modulated immunity the prevailing level of T-cell activity can be greatly augmented by a further antigenic stimulus without the necessity for renewed exposure to BCG.

Site of action of serum factors that block delayed-type hypersensitivity in mice.

When mice have been rendered anergic by a large intravenous dose of sheep erythrocytes, their inability to mount a delayed-type hypersensitivity (DTH) reaction is not due to an absence of mediator cells, for these can be detected in the spleen by cell transfer. Nor is it due to disappearance of accessory cells (monocytes) from circulation. The serum of anergic mice contains blocking factors which are more abundant after absorption with antigen. Such factors are unable to inactivate the mediators of DTH in vitro, nor do they suppress a DTH reaction when introduced locally into the reaction site. They are active, however, when given intravenously to systemically sensitized mice, provided that the sensitized animal has an intact spleen. If the spleen has been removed or the recipients of sensitized cells have been treated with cyclophosphamide before cell transfer, blocking factors are no longer able to suppress a DTH reaction. Reasons are given for the belief that suppression of DTH in animals undergoing a vigorous antibody response is due to the diversion of reactive cells from circulation to undertake an alternative role in antibody formation in the spleen.

The modifying effect of BCG on the immunological induction of T cells.

The inhibition of activated T cells by products of the humoral immune response is almost abolished by systemic infection with BCG. As a result, BCG-infected mice develop very high levels of delayed-type hypersensitivity (DTH) in response to doses of sheep red blood cells (SRBC) that cause complete suppression of DTH in normal mice. This systemic effect of BCG is dose-dependent, and lasts for about 3 wk. Its main effect is to counteract the inhibition of T cells by products of the humoral response. As a result, and in contrast to the T-cell-potentiating effects of cyclophosphamide (CY) which depend on a diminished production of antibodies, increased levels of DTH in BCG-infected mice are associated with increased antibody production. Since BCG and CY act in different ways, their effects are additive. Very remarkable levels of DTH are achieved when they are used in combination.

Restoration of cell-mediated immunity to animals blocked by a humoral response.

The T cells which mediate delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) are blocked by a normal humoral response and cannot be made to function by further immunization. They can be rescued to some extent by treatment with immunopotentiating agents such as cyclophosphamide (CY) which suppresses the antibody response selectively, or by BCG which interferes with the action of serum blocking factors. These two agents together can restore cell-mediated immunity completely, but a further antigenic stimulus is needed to reestablish DTH in mice blocked by a long period of continuous exposure to SRBC.

Potentiation of T-cell-mediated immunity by selective suppression of antibody formation with cyclophosphamide.

Delayed-type hypersensitivity (DTH) appears in mice immunized with less than an optimal immunogenic dose of sheep red blood cells (SRBC), but is blocked progressively as antibody production increases in response to larger doses of SRBC. Treatment with cyclophosphamide (CY) was shown to release T cells from this inhibitory influence of the humoral response, and cause enhancement of DTH. The magnitude of this enhancing effect on T-cell activity was markedly dependent on the time of treatment relative to the time of immunization, and on the time chosen for measuring DTH. The reasons for these pronounced effects of timing are threefold: (a) CY given before antigenic stimulation has a long-lasting effect on antibody formation, but no apparent effect on the precursors of activated T cells. (b) After antigenic stimulation, T cells also become susceptible to CY. (c) The production of a nonspecific participant (monocyte) in the DTH reaction is also suppressed by CY, though the supply of circulating monocytes is not immediately affected by the drug. The differential effect of CY on T and B lymphocytes depends on the differing physiological states of the majority of cells that make up these two populations. The former are resting cells that are insensitive to CY until exposed to specific antigen, while the latter are drawn from a rapidly replicating precursor pool and are susceptible to CY at all times.

Influence of dose and route of antigen injection on the immunological induction of T cells.

Delayed-type hypersensitivity (DTH) develops in the absence of an adjuvant when mice are injected intravenously or subcutaneously with an appropriate dose of sheep red blood cells (SRBC). The optimal intravenous dose of 10(5) SRBC (in CD-1 mice) produces maximum DTH which decays exponentially from its peak on day 4. Increasing the dose of SRBC reduces and eventually abolishes all evidence of DTH. DTH fails to reappear in respose to secondary stimulation except in splenectomized mice in whom the development of DTH is not suppressed, even by massive doses of SRBC. Hence the suppression cannot be due to antigen as such. The optimal dose of SRBC for sensitization by footpad inoculation is 100-fold higher (10(7) SRBC in CD-1 mice), but even 10(9) SRBC do not block the induction of DTH by this route of immunization. A blocking dose of SRBC, given intravenously 1 day before footpad inoculation, completely suppresses cell proliferation in the draining lymph node, prevents PFC production there, and blocks the induction of DTH by a sensitizing dose of SRBC. If given 1 day after footpad sensitization, intravenous antigen has little effect on the cellular response in the regional node but DTH is still completely suppressed. Blocking of induction and expression may depend, therefore, on different mechanisms.

Feedback inhibition of specifically sensitized lymphocytes.

An explanation was sought for the fact that delayed-type hypersensitivity (DTH) does not normally occur in response to T-cell-dependent antigens unless an adjuvant is used. But when sheep red blood cells (SRBC) were administered intravenously DTH did appear, provided that the dose of antigen was less than that required to give a maximum antibody response. Animals in which T-cell activity had been blocked by a large dose of antigen could not be sensitized adoptively, and their spleen cells failed to transfer DTH to normal recipients. The serum of blocked animals partially inhibited the induction of DTH, and after absorption with SRBC its blocking activity increased substantially. Moreover, absorbed serum inhibited DTH in previously sensitized animals, but it did not inhibit the proliferative response to SRBC in peripheral lymph nodes or reduce the number of plaque-forming cells produced therein. On the contrary, the hemagglutinating titer was actually increased by blocking serum even though DTH was totally suppressed. It is concluded that a product of the interaction between antigens and antibody blocks the activated T cells which mediate DTH without interfering with helper cells.

Multicenter evaluation of a transcription-reverse transcription concerted assay for rapid detection of mycobacterium tuberculosis complex in clinical specimens.

A European multicenter study was performed to evaluate the performance of a new method, based on the transcription-reverse transcription concerted reaction (TRC-2), which enabled one-step amplification and real-time detection of the Mycobacterium tuberculosis 16S rRNA target directly in clinical specimens. A total of 633 respiratory and nonrespiratory specimens were tested, and the results were compared with those from smears and cultures. A total of 129 patients (Paris center) were followed up in order to evaluate the clinical performance of TRC-2. By using M. tuberculosis complex strains to inoculate sterile sputa, the detection limit of TRC-2 was found to be 30 to 50 CFU/ml. A total of 548 respiratory specimens and 59 extrapulmonary specimens were assessable. For pulmonary specimens, the sensitivities of TRC-2 and acid-fast smear were 86.8% and 50.4%, respectively (P = 0.002). The specificities were 97.5% and 100%, respectively. For extrapulmonary specimens, the sensitivities of TRC-2 and acid-fast smear were 83.3% and 8.3% (P < 0.0001), and the specificities were 95.8% and 100%, respectively. Fifteen of 129 patients were diagnosed with pulmonary tuberculosis (TB). The sensitivities of culture and TRC-2 were 80% (12/15) and 86.7% (13/15) (P = 0.16), and the specificities were 100% and 93.9%, respectively. Based on an 11.6% incidence of TB in our population, the positive predictive values of TRC-2 and culture were 81.3% and 100%, respectively, and the negative predictive values were 98.2% and 97.4%, respectively. These results demonstrated that detection of M. tuberculosis complex in clinical specimens by TRC-2 with ready-to-use reagents was an efficient and rapid method for the diagnosis of pulmonary and extrapulmonary TB.

IFNgamma and antibody responses among French nurses during a tuberculosis contact tracing investigation.

STUDY: A comparative study which compared PPD skin testing inserted according to the French Society of Pneumology's recommendations and interferon gamma release assay (IGRA) (QuantiFERON((R)) TB Gold In-tube, QF-TB-IT, Cellestis, Carnegie, Australia) was performed during a tuberculosis contact investigation in our hospital. PATIENTS: Nineteen French health-care workers (HCWs) volunteered to participate. All of the HCW enrolled were BCG vaccinated and had a normal chest X-ray at entry. RESULTS: Among the HCW, 68.4% were TST positive. By comparison, only 31.6% had a positive QF-TB-IT result. We took advantage of the negative tube and the corresponding plasma for antibody detection by ELISA. None were ELISA positive. Fourteen HCWs were followed up. None of the HCWs accepted a course of antiTB chemoprophylaxis. Despite the difficulty in establishing a trend in kinetics, we saw the complexity of interpretation of a dynamic T-cell response after contact with an index case. CONCLUSION: This initial and first French picture provides us with the observation that only 44% of TST-positive HCW were IGRA positive, and the IGRA test allowed the detection of LTBI in two TST negative HCWs.

[Advantages and drawbacks of in vitro Interferon-gamma/T cell assays compared to the Mantoux test for the diagnosis of tuberculosis]. / Avantages et limites des tests sanguins in vitro lymphocytes T/interféron gamma comparativement au test intradermique à la tuberculine pour le diagnostic de tuberculose.

The development of in vitro blood tests that measure the delayed hypersensitivity reaction developed after contact with Mycobacterium tuberculosis will change progressively the diagnosis of M. tuberculosis infection. These blood assays (Quantiferon TB Gold, Cellestis, Australia; T-SPOT.TB, Oxford Immunotec, United Kingdom) use specific, complex M. tuberculosis antigens (ESAT-6 and CFP-10), whereas the intra-dermal Mantoux test is done with tuberculin, a complex mixture of more than 200 antigens. ESAT-6 and CFP-10 are absent from all the BCG vaccine strains used throughout the world. Significant improvement in the specificity with equivalent or increased sensitivity of the in vitro tests compared to the Mantoux test will lead eventually to replacement of the latter.

[New immunological tests in the diagnosis of tuberculosis]. / Les nouveaux tests immunologiques dans le diagnostic de la tuberculose (TB or not TB).

INTRODUCTION: Targeted testing and treatment of individuals with latent tuberculosis infection (LTBI), at high risk of progression to active tuberculosis (ATB), are key elements in the battle against tuberculosis, both in France and in many parts of the world. Though the finding of tubercle bacilli is the essential examination for the diagnosis of ATB, there is no indisputable test for LTBI. BACKGROUND: The help currently given to the diagnosis of LTBI by the degree of positivity of the tuberculin skin test (TST) is limited, both operationally and logistically, in populations vaccinated with BCG or sensitised by atypical mycobacteria, and by its low sensitivity in those immuno-suppressed persons who are at greatest risk of progression. Moreover the TST has other operational limitations linked to return visits, repeat testing causing a boosting effect and subjective interpretation. A new approach follows the availability of two biological tests for the diagnosis of LTBI (QuantiFERON-TB and T-SPOT-TB) that measure the in-vitro production of interferon gamma (IFN-gamma) by the blood mononuclear cells in response to M. tuberculosis specific antigens (ESAT-6 and CFP10). This revue analyses the published studies, undertaken with varying numbers of patients, that evaluate the diagnostic accuracy of these two tests in comparison with TST. However, validation is handicapped by the lack of a "gold standard" for the diagnosis of LTBI. These studies demonstrate similar levels of specificity for the two biological tests. They are statistically higher than those for TST, particularly in populations vaccinated by BCG. On the other hand, their sensitivity was at least equivalent to that of TST and, in certain studies, superior with T-SPOT-TB. Finally, several studies in contacts have been undertaken with the aim of measuring the concordance between these biological tests and TST. The essential finding is of a very good correlation between positivity of the biological tests and the degree of exposure of the contacts. These tests have additional operational advantages over TST: completed in one visit, results available in 24 hours, absence of inter and intra observer divergence, detection of potential immuno-depression and avoidance of boosting by repeat testing. VIEWPOINT: Currently, however, these biological tests present several operational limits: lower sensitivity in severe disease, incomplete data in immuno-suppressed subjects and in children, lack of predictive value for future development of ATB, lack of distinction between LTBI and ATB. Numerous clinical studies are under way, in France and elsewhere, in order to reduce these limitations and to allow the appropriate incorporation of these tests into protocols for the diagnosis of tuberculosis. CONCLUSIONS: These two biological tests should, in the near future, replace or complement TST in the diagnosis of recent LTBI, leading to their optimal incorporation into the decision making processes of the national plans for the control of tuberculosis.

In vivo antitumor activity of various forms of delayed-type hypersensitivity in mice.

Relationships among various forms of delayed-type hypersensitivity (DTH) and nonspecific resistance to Lewis lung tumor were studied in syngeneic and semisyngeneic mice. Only the tuberculin type of DTH obviated a virulent inoculum of 10(6) tumor cells. The Jones-Mote type of DTH, even modified by cyclophosphamide pretreatment, produced a significant local inflammatory reaction which was unable to destroy tumor cells. The antitumor effect of the tuberculin type was observed in BCG-or in Corynbacterium parvum-immune mice and also in sheep red blood cell-immunized mice, but only after the modulating effect of BCG. The antitumor activity of the DTH reaction was anatomically restricted and time related, and it required local persistence of specific antigen. A minimal number of bacteria, 1 times 10(6) living or heat-killed BCG organisms, were equally able to eradicate 10(5) tumor cells in BCG-immune mice. Biphasic effects on tumor growth were observed when systemic specific inflammatory reactions were elicited in BCG-immune mice. However, tumor-specific immunity was never observed, inasmuch as BCG-immune mice surviving injection of a mixture of BCG and tumor cells did not resist a second tumor cell challenge.

[The role of human dendritic cells in tuberculosis: protector or non-protector?]. / Rôle des cellules dendritiques humaines dans la tuberculose: protecteur ou non protecteur?

INTRODUCTION: Mycobacterium tuberculosis, the cause of tuberculosis remains a pathogenic organism capable of infecting a large number of individuals and of resisting the immune response of the infected host. The main constituents of this response are the antigen presenting cells such as dendritic cells, macrophages and T lymphocytes. BACKGROUND: Comparative study of the interactions between M. tuberculosis and the antigen presenting cells has shown that dendritic cells do not permit intracellular growth of M. tuberculosis, unlike that seen in macrophages. A hostile intracellular compartment creates a bacteriostatic environment. M. tuberculosis is internalised by binding to a C-type lectin receptor (DC-SIGN). VIEWPOINT: This receptor recognises polysaccharide compounds on the surface of M. tuberculosis. This sugar-lectin bond may compensate for the bond between bacterial compounds and Toll receptors, partially inhibiting the protective inflammatory reaction or compensating for an excessive inflammatory reaction. CONCLUSIONS: This bond encourages both the persistence of quiescent bacteria in the dendritic cells and the reciprocal adaptation of the host and the bacteria over the course of time.

[Antiviral vaccination and respiratory mucosal immunity: still disappointing results from a seductive idea]. / Vaccination antivirale et immunité muqueuse respiratoire: un concept séduisant pour des résultats encore décevants.

Mucosal surfaces of the respiratory tract represent a major portal of entry for most human viruses and a critical component of the mammalian immunologic repertoire. The major antibody isotype in external secretions is secretory immunoglobin A (S-IgA). The major effector cells in mucosal surfaces, however, are not IgA B cells, but T lymphocytes, which may account for up to 80% of the mucosal lymphoid cell population. Mucosal immunoprophylaxis is theoretically an important approach to control infections acquired through these portals. Passive antibodies can protect against mucosal viral infections, as shown for respiratory syncytial virus, but very high quantities of passive antibodies are needed to restrict virus replication on mucosal surface. Factors likely to induce mucosal antibody and cell-mediated immune responses include oral or respiratory routes of immunization and active (effectively replicating) vaccine agents. Very few antiviral vaccines have been developed to protect the mucosal surface of the respiratory tract, and only an attenuated influenza virus vaccine uses the nasal route. Other vaccines, approved for parenteral use, have been administered experimentally by the nasal route; these include active (replicating) and inactive (nonreplicating) vaccines. By this route they induce only a moderate local mucosal response. Neither the development of mucosal immunity nor the administration of vaccines via the mucosal route is essential for control or prevention of most respiratory viral infections and diseases acquired through the respiratory tract. Nonetheless, the example of the live attenuated intranasal influenza vaccine, which induces both systemic and local immune response, is promising for the future of mucosal immunization against respiratory viral infections.

False-positive HIV antigens related to emergence of a 25-30 kD protein detected in organ recipients.

OBJECTIVE: The routine screening of organ donors for HIV-1 since 1985 has markedly reduced the risk of acquiring infection in organ recipients. However, commercial HIV-1 p24-antigen assays reveal false-positive reactivity in certain recipients. This observation will be discussed here. METHODS: Post-transplantation sera collected sequentially from different organ recipients were tested for HIV antigen: 79 samples were from 14 kidney recipients, 57 from seven bone-marrow allografts and 18 from two heart recipients. Neutralization assays to determine specificity were performed on reactive samples. Immunoblots prepared from sera containing high levels of antigens were tested by Western blot using polyclonal anti-HIV sera. RESULTS: Abbott HIV-1-EIA kits detected non-neutralizable antigens in early post-transplantation sera from 12 kidney, five bone-marrow and two heart recipients. Using in-house immunoblots prepared from positive non-neutralizing antigen sera, a 25-30 kD protein was detected and shown to be the cause of the false HIV antigen cross-reactivity. CONCLUSION: False-positive HIV antigens related to the emergence of a 25-30 kD protein in early post-transplantation sera are detectable in transplant recipients.

Campylobacter infections in HIV-infected patients: clinical and bacteriological features.

OBJECTIVE: To study the clinical and bacteriological features of Campylobacter infections in HIV-infected patients. DESIGN: A retrospective analysis (1989-1992), followed by a prospective analysis (1992-1994). SETTING: Hospital HIV inpatient unit. PATIENTS AND METHODS: All patients with Campylobacter spp. identified by the laboratory of microbiology at Saint-Louis Hospital, Paris were studied, and their clinical features as well as their response to therapy recorded. RESULTS: During the study period, Campylobacter infection was documented in 38 HIV-infected patients, 76% of whom had AIDS. Campylobacter spp. was isolated from stools in 36 cases and from blood cultures in four cases. Species identification yielded C. jejuni (84%) and C. coli (16%). High-level resistance to quinolones was frequently observed (21%), but resistance to erythromycin (3%) and tetracycline (5%) was rare. Diarrhoea, fever and abdominal pain were the main clinical features of infection. Other intestinal pathogens were found in 42% of patients. Most patients had an acute illness with rapid resolution under appropriate antimicrobial therapy. However, eight patients (21%), experienced chronic diarrhoea with persistent isolation of Campylobacter and in vivo selection of resistant strains, requiring multiple courses of antibiotics. CONCLUSIONS: Campylobacter usually cause acute diarrhoea in patients with HIV infection. Antimicrobial therapy should be guided on in vitro susceptibility testing because of the prevalence of antibiotic resistance. Despite appropriate therapy, some patients will present with prolonged diarrhoea and in vivo selection of multiresistant isolates.

Risk factors for Clostridium difficile-associated diarrhoea in HIV-infected patients.

OBJECTIVE: To identify risk factors associated with a first episode of Clostridium difficile-associated diarrhoea (CDAD) in patients with HIV infection. DESIGN: A case-control study. SETTING: University teaching hospital HIV inpatient unit. PATIENTS AND METHODS: Nineteen HIV-infected patients with CDAD, defined as diarrhoea with positive stool culture for Clostridium difficile (CD) and positive stool cytotoxin B assay, were compared with 38 randomly selected controls (HIV-infected patients hospitalized on the ward on the day the matched case was diagnosed). CD isolates were phenotyped by electrophoretic protein patterns. RESULTS: The incidence of CDAD among HIV-infected patients was 4.1/100 of patient-admissions. On univariate analysis, cases were more likely to have used clindamycin [11 out of 19 compared with four out of 38; odds ratio (OR) 19; 95% confidence interval (CI), 2-160; P = 0.0007], and pyrimethamine (14 out of 19 compared with 13 out of 38; OR, 4.8; 95% CI, 1.4-16, P = 0.02) in the month before diagnosis, and to have had cerebral toxoplasmosis (12 out of 19 compared with 13 out of 38; OR, 2.8; 95% CI, 0.9-8.6; P = 0.09). There was also a significant increase of the risk of CDAD as duration of hospitalization in the ward increased (chi 2 for trend, P = 0.007). Multivariate models associated two risk factors with CDAD: clindamycin use (OR, 42; 95% CI, 2-813; P = 0.01), and prolonged hospitalization in the ward (OR, 3.6 per week in the ward; 95% CI, 1-13, P = 0.048). Of 18 available CD isolates, 15 (83%) had identical electrophoretic protein pattern. CONCLUSIONS: Clindamycin use and prolonged hospitalization in the ward were the main risk factors associated with CDAD in this study. These observations, together with the occurrence of one major phenotype of CD, suggest nosocomial transmission of CD in the ward.

Superoxide anion production during monoelectronic reduction of xenobiotics by preparations of rat brain cortex, microvessels, and choroid plexus.

Brain microsomes may produce reactive metabolites during the reductive metabolism of some xenobiotics including drugs. These reactive species can, in turn, react with molecular oxygen to form superoxide radicals (O2.-). We measured the rates of superoxide production by homogenates obtained from three cerebral structures, cortex plus cerebellum, choroid plexus, and microvessels. The molecules assayed were related to quinone, nitroheterocycle, and iminium chemical families. The results we obtained showed a significant correlation between the rate of superoxide anion production and the apparent kinetic parameters (log Km/Vmax) of NADPH-cytochrome P450 reductase activity for these molecules, suggesting the involvement of this enzyme in xenobiotic-induced superoxide production.

Transendothelial permeability changes induced by free radicals in an in vitro model of the blood-brain barrier.

In the present study, we investigated the changes in blood-brain barrier (BBB) permeability following brain endothelial cell exposure to different xenobiotics able to promote free radical generation during their metabolism. Our in vitro BBB model consisted of confluent monolayers of immortalized rat brain capillary endothelial cells (RBE4) grown on collagen-coated filters in the presence of C6 glioma cells grown in the lower compartment. We have recently shown that a range of xenobiotics, including menadione, nitrofurazone, and methylviologen (paraquat) may undergo monoelectronic redox cycling in isolated brain capillaries, giving rise to reactive oxygen species. In this study, addition of 100 microM menadione to the culture medium for 30 min significantly increased the permeability of endothelial cell monolayers to radiolabeled sucrose. The effect on endothelial permeability induced by menadione was dose-dependent and reversible. These permeability changes preceded the onset of cell death, as assessed by the Trypan blue exclusion method. Pre-incubation with superoxide dismutase and catalase blocked changes in sucrose permeability to control levels in a dose-dependent manner, suggesting the involvement of reactive oxygen species in menadione-induced BBB opening.

Cerebral tuberculosis in patients with the acquired immunodeficiency syndrome (AIDS). Report of 6 cases and review.

Cerebral tuberculosis (TB) was diagnosed in 6 (4%) of 156 HIV-infected patients with TB seen at our institution over 6 years. We describe here the clinical and radiologic features of these cases and of 15 others reported in the literature. Of the 21 patients, 59% were intravenous drug users. Presenting symptoms were fever (76%), confusion (52%), seizures (38%), and headache (38%). Fourteen patients (66%) had previous or active extracerebral TB at presentation. Cranial CT scan showed ring-(62%) or nodular-(24%) enhancing lesions or mixed forms (14%). Among the 12 patients who underwent a brain biopsy, bacteriologic evidence of TB was found in 9. Four patients (19%) died during hospitalization. Among the 17 others who received antituberculous therapy, only 1 developed neurologic sequelae. Five patients also received steroid therapy to control cerebral edema or paradoxical growth of the cerebral mass lesions. TB should be considered as a cause of cerebral mass lesions in HIV-infected patients, especially if tuberculous infection is suspected at other sites.