Need for an external proficiency testing program for cytokines, chemokines, and plasma markers of immune activation.

An external evaluation program for measuring the performance of laboratories testing for cytokines and immune activation markers in biological fluids was developed. Cytokines, chemokines, soluble cytokine receptors, and other soluble markers of immune activation (CSM) were measured in plasma from a healthy human immunodeficiency virus (HIV)-seronegative reference population and from HIV-seropositive individuals as well as in supernatant fluids from in vitro-stimulated human immune cells. The 14 components measured were tumor necrosis factor (TNF) alpha, gamma interferon, interleukin-1 (IL-1), IL-2, IL-4, IL-6, IL-10, Rantes, MIP-Ia, MIP-Ibeta, soluble TNF receptor II, soluble IL-2 receptor alpha, beta(2)-microglobulin, and neopterin. Twelve laboratories associated with the Adult and Pediatric AIDS Clinical Trial Groups participated in the study. The performance features that were evaluated included intralaboratory variability, interlaboratory variability, comparison of reagent sources, and ability to detect CSM in the plasma of normal subjects as well as the changes occurring in disease. The principal findings were as follows: (i) on initial testing, i.e., before participating in the program, laboratories frequently differed markedly in their analytic results; (ii) the quality of testing of a CSM in individual participating laboratories could be assessed; (iii) most commercial kits allowed distinction between normal and abnormal plasma CSM levels and between supernatants of stimulated and unstimulated cells; (iv) different sources of reagents and reference standards frequently provided different absolute values; (v) inexperienced laboratories can benefit from participating in the program; (vi) laboratory performance improved during active participation in the program; and (vii) comparability between analyses conducted at different sites can be ensured by an external proficiency testing program.

Distinct categories of immunologic changes in frail elderly.

Immune changes and their relationships in a frail elderly population (N=116, age 70-103, median 86 years) were defined in comparison to a healthy younger group. Previous immune studies in the elderly have generally focused on one or few parameters without correlation analyses. Furthermore, the study populations have been active elderly in relatively small numbers. A total of 33 immune parameters representing many aspects of the immune system were quantified. Most changes in the frail elderly were parallel to those reported in active elderly. A classification tree analysis revealed that increased plasma activation markers (neopterin and sTNF-R) and increased CD28 expression on CD8 T cells and proliferative response separated the aged and control populations. Statistical procedures utilizing principal components analyses, partial correlations and exploratory factor analyses all indicated that immunologic parameters in frail elderly are grouped in three major clusters of immunologic results. These involved (a) increased plasma levels of neopterin and sTNF receptor indicating elevated IFNgamma and TNF cytokine activity; (b) increased proportion of mature (CD45RO) versus naïve (CD45RA) T cells; and (c) a diverse group of related changes including impaired proliferative response, reduced T cells, CD28 and CD25 expression, B cell percentage and lower CD4:CD8 ratios and increased HLA-DR expression. These findings emphasize that several different groups of immune parameters but not 33 independent immune changes, occurred in the aged population.

Stability of plasma levels of cytokines and soluble activation markers in patients with human immunodeficiency virus infection.

Cytokine and immune activation marker levels in plasma are valuable measurements of immune status and treatment effects in human immunodeficiency virus (HIV) infection and AIDS. Five populations representing various stages of disease were studied: controls, 2 AIDS groups with <50/mm3 CD4 cells, and 2 groups of HIV-positive subjects-1 with stable CD4 T cells (median, 545/mm3) and 1 with >100/mm3 CD4 cell decline in 1 year. Relatively stable levels of tumor necrosis factor (TNF)-alpha, soluble TNF receptor (R)II, soluble interleukin-2R, neopterin, and beta2-microglobulin (beta2M) were documented over 5-8 weeks in patients with AIDS and for 1-4 years in the other groups. beta2M was generally the most stable marker. Interferon-gamma levels, however, fluctuated substantially. Individuals, whether normal or HIV-positive, maintain characteristic plasma levels of cytokines and immune activation markers. Thus, documented changes, in excess of the variability observed in this study, are likely to be significant indicators of change in disease status or effects of therapy.

The prognostic significance in HIV infection of immune activation represented by cell surface antigen and plasma activation marker changes.

One hundred and eighteen HIV-infected homosexual men without AIDS and 40 control seronegative homosexual men were assessed for 23 parameters reflecting immune activation to determine prognostic significance for occurrence of AIDS. Samples cryopreserved in 1987-1989 were analyzed, with AIDS occurrence determined by mid-1992. Cell surface antigens assessed on the major lymphocyte subsets were HLA-DR, CD38, CD71, and CD25. Soluble serum molecules assessed were tumor necrosis factor alpha, soluble TNFalpha receptor II, soluble IL-2 receptor alpha, neopterin, and beta2-microglobulin. Using a proportional hazards model, prognostic markers included decreased CD4 number and percentage; increased sIL-2R, neopterin, and beta2M; increased percentage HLA-DR+ total lymphocytes and CD4+ cells; increased CD38+ total lymphocytes and CD8+ cells; increased CD71+ total lymphocytes and CD4+ cells; and decreased CD25+ total lymphocytes and CD19+ cells. After adjustment for CD4 cell levels, sIL-2R, neopterin, beta2M, and CD25+ CD19 cells remained significant, indicating that additional information about AIDS risk was provided by these markers.

Variables that affect assays for plasma cytokines and soluble activation markers.

Cytokines and soluble immune activation markers that reflect cytokine activities in vivo are increasingly being measured in plasma, serum, and other body fluids. They provide useful diagnostic and prognostic information as well as insight into disease pathogenesis. Assays of neopterin, beta2-microglobulin, soluble interleukin-2 receptor, and soluble tumor necrosis factor receptor type II as well as of the cytokines tumor necrosis factor alpha and gamma interferon (IFN-gamma) were evaluated by using serum and plasma samples of human immunodeficiency virus (HIV)-positive and HIV-negative subjects. Many factors were found to influence the outcomes of these assays. Substantial differences in apparent levels of analytes were frequently found when enzyme-linked immunosorbent assay (ELISA) kits from different manufacturers were used. In some cases, differences were found in the standards provided by separate manufacturers. Furthermore, the analytic results from different lots of ELISA kits supplied by single manufacturers differed by as much as 50%. The need for uniformity in the standards for quantitative assays was clearly illustrated. International reference standards are available for cytokines but not for soluble cytokine receptors or soluble activation markers. Marker levels in serum or in plasma were similar except those for IFN-gamma. Most of the analytes were stable under several storage conditions. Thus, batch testing of frozen stored samples is feasible. The findings indicate that for longitudinal studies, the levels of cytokines and immune activation markers in plasma or serum should be measured by using preverified reagents from one manufacturer. The quality of laboratory performance can have an impact on clinical relevance. Proficiency testing and external quality assurance programs can help to develop the needed consensus.

Phenotypic and functional characteristics of circulating monocytes of elderly persons.

Aging is associated with impairment of immune functions. Age-dependent alterations in T-cells are well known. Although the pivotal role of monocytes in immune regulation by their production of proinflammatory and inhibitory cytokines is acknowledged, limited information is available on monocyte changes in aging. The present study focused on phenotypic changes in circulating monocytes in elderly subjects and in the level of cytokines they produce. The results demonstrated a significant expansion of CD14dim/CD16bright circulating monocytes in elderly. In contrast, the majority of circulating monocytes of healthy young individuals were CD14bright/CD16dim. The CD14dim/CD16bright monocytes are considered to have phenotypic evidence for activation. Furthermore, significant increases of constitutive production of monocytic cytokines including interleukin (IL)-1beta. IL-1 receptor antagonist, and IL-6 by nonstimulated monocytes from elderly was also indicative of activation. This was also observed when monocytes from elderly were cultured with autologous lymphocytes. However, after stimulation, significantly lowered IL-1beta production was observed and IL-6 and IL-10 tended to be higher in the elderly. Collectively, these results indicate that monocytes of aged individuals, in contrast to a younger population exhibit in vivo activation as well as imbalanced production of cytokines. Such age-related alterations in monocytes may contribute to impaired immune competence of aging.

Levels of cytokines and immune activation markers in plasma in human immunodeficiency virus infection: quality control procedures.

Procedures for quality control (QC) in a laboratory that concentrates on cytokine and soluble marker measurements in biological fluids are outlined. Intra-assay, interassay, and interlaboratory experiences are presented. Plasma and serum beta2-microglobulin (beta2M) and neopterin test data are presented in greatest detail, along with substantial tumor necrosis factor alpha (TNF-alpha), gamma interferon, soluble interleukin-2 receptor-alpha (sIL-2Ralpha), sTNF-RII, IL-4, and IL-6 data. Recommended QC procedures for cytokine and soluble-marker testing include replicate testing of two or more reference samples provided by the kit manufacturer, replicate testing of in-house frozen reference QC samples that represent normal and abnormal analyte contents, retesting 15 to 20% of randomly selected samples, and comparing normal reference ranges each year. Also, eight cytokines and soluble markers were evaluated in human immunodeficiency virus (HIV)-seronegative and HIV-seropositive individuals stratified on the basis of CD4 T-cell numbers. Levels of some but not all cytokines in serum increased in HIV infection. There was a tendency for cytokines to increase with more advanced disease, defined by reduced CD4 T-cell numbers. Cytokine changes did not relate closely to CD4 level, indicating that separate information was provided by the measurements of TNF-alpha, sTNF-RII, sIL-2Ralpha, beta2M, and neopterin. Serum IL-4 and TNF-alpha levels were not increased. The quality of laboratory data can impact on clinical relevance. Interlaboratory comparisons revealed substantial differences at some sites and documented the need for external proficiency-testing quality assurance programs.

Prognostic significance of plasma markers of immune activation, HIV viral load and CD4 T-cell measurements.

OBJECTIVE: To evaluate the prognostic significance for AIDS occurrence of plasma levels of immune activation markers in comparison with and in conjunction with HIV viral load and CD4 T-cell measurements. DESIGN: A retrospective analysis was conducted of three plasma activation markers, the soluble tumor necrosis factor (TNF) receptor II (TNF-RII), neopterin and soluble interleukin-2 receptor levels, and of CD4 T-cell levels and plasma HIV viral load. SUBJECTS: The participants were 659 men taking part in the University of California Los Angeles Multicenter AIDS Cohort Study who were HIV-seropositive but AIDS-free in 1985. MAIN OUTCOME MEASURE: Clinically defined AIDS within 3 years. Failure time statistical regression models for the time to development of AIDS were used to assess prognostic capacity of the parameters alone and in combination. RESULTS: All the markers had prognostic capability. The levels of the three plasma activation markers correlated well with each other (median r = 0.61). They related less well with HIV RNA plasma levels (median r = 0.50) and least well with CD4 cell levels (median r = 0.36). Furthermore, plasma marker levels were shown to be able to stratify patients for prognosis within all the major categories of CD4 T-cell and HIV RNA levels. CONCLUSIONS: Plasma levels of soluble TNF-RII and other soluble markers of immune activation have prognostic capabilities which are different from HIV and CD4 T-cell levels. Combination of a single plasma activation marker measurement (such as soluble TNF-RII) with CD4 T-cell levels improved the prognostic capability of each. A new graphic technique for presenting prognostic capability indicated that plasma soluble TNF-RII and CD4 cell levels are better prognostic factors than HIV plasma level with CD4 cells < 200 x 10(6)/l. Inexpensive tests for one of the plasma activation markers, such as soluble TNF-RII or neopterin, can be useful for evaluations of HIV disease course, especially when expensive equipment, technical expertise and funding required for flow cytometry and for HIV load measurements are not readily available.

Increased immune activation precedes the inflection point of CD4 T cells and the increased serum virus load in human immunodeficiency virus infection.

The temporal relationship of serum levels of human immunodeficiency virus (HIV) RNA and of immune activation products in 10 HIV-seropositive persons who showed an accelerated decline (inflection point) in CD4 T cell counts and went on to develop AIDS and in 10 matched controls without inflection point were examined. Cases and controls did not differ statistically at the baseline time point for this study. CD4 cell inflection points occurred 18-30 months before AIDS development. Serum levels of soluble tumor necrosis factor receptor II, soluble interleukin-2 receptor, beta2-microglobulin, and neopterin increased significantly > or = 6 months before the CD4 cell inflection point. In contrast, increases in mean HIV RNA levels occurred at the time of the CD4 cell inflection point. These data are consistent with the view that in vivo immune activation precedes the increases in virus load and is followed by an accelerated and rapid loss of CD4 lymphocytes.

Oral fluids as an alternative to serum for measurement of markers of immune activation.

Oral fluids are convenient alternatives to blood sampling for evaluating significant metabolic components. Two forms of oral fluids, oral mucosal transudates (OMT) and saliva, were collected and compared for content of soluble products of immune activation. The data confirm that OMT and saliva represent distinct body fluids. The concentrations, outputs, and analyte/protein ratios of beta-2-microglobulin (beta2M), soluble tumor necrosis factor alpha receptor II (sTNFalphaRII), and neopterin were measured. Both the OMT and the saliva of most of the individuals in the control healthy populations had measurable levels of all three activation markers. When the immune system is activated, as in human immunodeficiency virus (HIV) infection, the levels of beta2M and sTNFalphaRII are increased in both OMT and saliva compared to those in a healthy control population. OMT levels correlated better with levels in serum than did saliva and appear to reflect systemic immune activation in HIV infection. Because acquisition of oral fluids is noninvasive and easily repeatable, measurement of beta2M and/or sTNFalphaRII content in OMT could be useful in the assessment of disease activity in patients with HIV infection or chronic inflammatory diseases.

Accelerated changes (inflection points) in levels of serum immune activation markers and CD4+ and CD8+ T cells prior to AIDS onset.

The trajectories of change in CD4+ and CD8+ lymphocytes and serum neopterin and beta2-microglobulin (beta2M) levels were determined in 158 HIV-seropositive individuals during 5.5 years before a clinical AIDS diagnosis. Each patient was evaluated separately using a two-piece regression model with seven possible change points to identify any adverse change (inflection point) in the slopes of each immunologic marker of HIV infection. Two categories of subjects were distinguished for each marker--those with statistically significant inflection points and those who demonstrated a steady progression of changes to AIDS. Fifty-nine percent had an inflection point for CD4+ T cells. The frequency of inflection points for CD8+ was 49%, for serum neopterin -48% and for beta2M -38%. Inflection points were found over a 4-year span. Three distinctive categories of inflection points were observed on the basis of their independent occurrence: one was in CD4+ T cells, another in CD8+ T cells, and a third in the serum markers of immune activation. The inflection point for CD4+ usually occurred prior to those for CD8+ T cells (p=.0002). The HIV-positive persons with inflection points were diagnosed with AIDS when immunologic parameters were significantly more abnormal than in those with steady progression (p < .0003). Thus, these two groups differed in the course of immune changes and in the levels of immune abnormalities associated with the occurrence of clinical AIDS.

Cytokine gene expression in normal human lymphocytes in response to stimulation.

Sequential gene expression of two type 1 cytokines (interleukin 2 [IL-2] and gamma interferon), one type 2 cytokine (IL-10), two monokines (IL-6 and tumor necrosis factor alpha), and one cytokine receptor (IL-2 receptor [IL-2R]) in normal human peripheral blood mononuclear cells (PBMC) following in vitro stimulation was investigated by reverse transcription-PCR methods. Two stimuli were utilized: phytohemagglutinin (PHA), which acts on the CD2 molecule and T-cell receptors, and anti-CD3 monoclonal antibody, which acts on the CD3 molecule and on T-cell receptors. Increased expression of all studied genes occurred between 1 and 4 hours after stimulation, except for that of the gene encoding IL-10, which was delayed. Expression of all but one of the genes was transient, with a maximal mRNA accumulation at about 8 h on average. IL-2R mRNA expression was an exception, showing a prolonged increase (72 h). The general profiles of expression of the five cytokine genes were similar but not identical, suggesting some shared regulatory mechanisms. When responses to four additional stimuli (pokeweed mitogen, Candida albicans, and IL-2 at high and low doses) were compared, similar profiles of cytokine gene expression were found. Thus, the various stimuli caused induction of all cytokines with quantitative, not qualitative, differences. Altogether, the present data are useful for defining the kinetics of gene expression for key cytokines in response to standard immune-cell stimuli.

Relation of impaired lymphocyte proliferative function to other major human immunodeficiency virus type 1-induced immunological changes.

Human immunodeficiency virus (HIV) type 1 (HIV-1) induces impairment of immune function reflected in reduced lymphocyte proliferative responses. Many other immune changes are induced by HIV-1, but their relationship to lymphocyte functional defects is not known. The present study was designed to correlate functional defects with other HIV disease parameters. Cryopreserved samples from 118 HIV-1-positive subjects and 40 seronegative individuals were examined. The main findings were that impaired proliferative responses to mitogens correlated with (i) decreased cell surface expression of the interleukin-2 receptor (CD25), (ii) increased expression of HLA-DR antigens on CD4 cells, (iii) reduced CD4 and increased CD8 cell numbers, and (iv) increased levels of serum immune complex dissociated p24 antigen. However, impaired function was not associated with increased serum neopterin, beta2-microglobulin, or soluble interleukin-2 receptor or with CD38 antigen expression on lymphocytes. In summary, proliferative functional impairment correlated with some, but not all, immunological changes associated with HIV-1 infection. Most of the phenotypic markers that correlated with altered function are cell surface molecules with significant roles in lymphocyte proliferation and were associated primarily with CD4 cells, compatible with the view that dysregulation of CD4 cells is responsible for impaired function.

HIV-1 gp120-specific antibody-dependent cell-mediated cytotoxicity correlates with rate of disease progression.

The Ab-dependent cell-mediated cytotoxicity (ADCC) activity of anti-gp120 Abs in serum from four groups of HIV-1-positive individuals in the Multicenter AIDS Cohort Study was evaluated at several time points over a 10-yr period. HIV-1-positive individuals who progressed to AIDS within 3 yr of seroconversion (rapid progressors) were compared with seroconverters who did not progress to AIDS within 6 yr (nonrapid progressors) and individuals who were seropositive when they entered the study and did not progress to AIDS within 9-10 yr (nonprogressors). At the visit closest to AIDS, rapid progressors had significantly lower titers of Abs that mediate ADCC against HIV-1 gp120 than those of nonrapid progressors at corresponding visits or those of nonprogressors at any visit. Nonprogressors generally had high titers of ADCC Abs at all visits. Differences between ADCC titers of rapid progressors and nonrapid progressors or nonprogressors remained when longitudinal changes within individuals were compared. Among seroconverters who were nonrapid progressors, those with low or declining ADCC titers lost significantly more CD4+ cells during the study than those whose ADCC titers were stable or increasing, even though both groups had similar serum virion RNA levels. This demonstrates that high titers of Abs that mediate ADCC correlate with a successful host defense against AIDS.

Induction of IL-6 and IL-10 production by recombinant HIV-1 envelope glycoprotein 41 (gp41) in the THP-1 human monocytic cell line.

Elevated levels of circulating monokines (IL-6, IL-1, and TNF alpha) have been seen in HIV-1 infection, and the overproduction of these cytokines could contribute to AIDS pathogenesis in various ways. In previous work, we had seen that exposure of human monocytes to HIV-1, including inactivated, noninfectious HIV, led to rapid IL-6 gene expression and secretion. To investigate cytokine production in response to components of HIV by monocytes/macrophages, production of IL-6 and IL-10 were examined in a human monocytic cell line, THP-1, stimulated by HIV proteins. IL-6 production was induced in THP-1 cells by a detergent lysate of HIV, particularly fractions at molecular weight of 25-50 kDa. Recombinant HIV envelope glycoprotein 41 (gp41), but not gp120 or p24, also was seen to induce significant IL-6 production by THP-1 cells. These results suggest that gp41, transmembrane protein, is the primary HIV-encoded protein involved in inducing IL-6 production. IL-10 was also produced with delayed kinetics, following IL-6 production in THP-1 cells stimulated by gp41. To investigate a possible regulatory role for IL-10 in HIV-induced monokine production, recombinant IL-10 was added to gp41-exposed THP-1 cells. IL-10 inhibited gp41-induced IL-6 production and reduced the expression of IL-6 mRNA. When anti-human IL-10 neutralizing antibody was added to THP-1 cells, IL-6 production was enhanced. These results suggest that the IL-6 production may be downregulated by endogenously produced IL-10 and that IL-10 may downregulate cytokine production by HIV-activated monocytes via an autoregulatory mechanism.

Characterization of immune suppression by a synthetic HIV gp41 peptide.

HIV infection is associated with immunosuppression leading to susceptibility to opportunistic infections and tumors. HIV proteins can be immunosuppressive with substantial activity residing within the gp41 portion of HIV envelope glycoprotein gp160. In this report, immunosuppressive properties of a synthetic peptide corresponding to amino acid sequence 584-609 of HIV-1 transmembrane protein gp41 were investigated. The peptide was found to inhibit proliferative responses of normal human lymphocytes to mitogens and recall antigen. Stimulations by IL-2 and by anti-CD3 were also inhibited, indicating that the effect occurred in a pathway of response shared by CD3 and by IL-2 receptor recognition systems. Both CD4 and CD8 T cells were suppressed, indicating that the suppression did not require interactions with CD4 molecules. Consistently, the peptide was suppressive in the presence of HIV-infected patients' sera containing specific antibodies to the peptide, suggesting that the active portion was probably not an immunogenic configuration. These in vitro results emphasize the likelihood that HIV gp41 contributes to the in vivo immunosuppression and immune dysfunction of HIV-infected persons.

Human immunodeficiency virus proteins induce the inhibitory cAMP/protein kinase A pathway in normal lymphocytes.

Proliferation of normal T lymphocytes is impaired by human immunodeficiency virus (HIV) proteins. In this paper, we demonstrate important parts of this mechanism. Initially, HIV-induced impairment of proliferation was shown to be an active process involving induction of protein tyrosine kinases in both CD4 and CD8 T cells. Furthermore, the impairment of cell proliferation was demonstrated to be linked to induction of the inhibitory protein kinase A (PKA) pathway by HIV proteins. This induction of PKA was accompanied by an increase in intracellular cAMP, which is necessary for the activation of PKA. Finally, increases in cAMP/PKA activity were shown to induce biochemical changes that impaired proliferation when cells were stimulated with phytohemagglutinin. This was demonstrated by showing that (i) agents, other than HIV proteins, that increase cAMP/PKA activity (cholera toxoid and 8-bromo-cAMP) also decreased T-lymphocyte proliferation; (ii) exposure of lymphocytes to HIV or cholera toxoid led to decreased membrane activity of the proliferation promoter protein kinase C upon stimulation; and (iii) agents that reduced cAMP generation neutralized the effect of HIV proteins and restored lymphocyte proliferation. These studies show that the HIV-induced augmentation of cAMP/PKA activity may be a key part of the mechanism responsible for all or part of the HIV-induced anergy of T lymphocytes.

Restoration of T-cell function in HIV infection by reduction of intracellular cAMP levels with adenosine analogues.

OBJECTIVE AND DESIGN: The impaired function of T cells is characteristic of HIV infection. It contributes to disease pathogenesis and is associated with disease prognosis. Our aim was to describe a biochemical basis for this impairment and a pharmacological way of restoring function. METHODS: Measurement of intracellular cAMP, protein kinase A (PKA) activity and proliferative capacity of T cells to recall antigens. RESULTS: HIV-seropositive individuals without AIDS showed significant increases in intracellular cAMP levels and PKA activity (inhibitors of lymphocyte function). The proliferative capacity of T cells to recall antigens correlated inversely with initial cAMP levels: poor proliferation was associated with high cAMP level in HIV infection. Moreover, drugs that reduced intracellular cAMP levels led to significant restoration of specific T-cell proliferation and cytotoxicity. CONCLUSIONS: Our findings indicate that high intracellular cAMP concentrations contribute to pathogenesis of T-cell anergy in HIV infection and that drugs that decrease intracellular cAMP levels may be beneficial in the treatment of AIDS.

Immune changes in HIV-1 infection: significant correlations and differences in serum markers and lymphoid phenotypic antigens.

Human immunodeficiency virus type 1(HIV-1) induces extensive immune cell alterations which can be detected by changes both in serum levels of soluble immune activation products and in several lymphoid phenotypic markers. The current studies were conducted in 70 HIV-1 seropositive subjects to determine whether changes among four important serum immune activation markers (neopterin, beta-2 microglobulin, soluble CD8, and soluble IL-2 receptor) and seven lymphoid phenotypic markers (CD38, HLA-DR, CD57, CD11b, CD45RA, leu8, and CD71) reflect similar or disparate aspects of immune pathology. On the basis of correlation coefficient calculation, four groups of related markers (Fig. 1) were identified: Group A, sIL-2R was related to group B where serum neopterin, beta 2M, sCD8 levels, and lymphocyte CD38 antigen expression correlated closely. Loss of CD45RA or Leu 8 antigens in group C correlated with group B and D markers increase. HLA-D in group D was a more distantly related immune activation marker. Phenotypic markers CD57, CD11b, and CD71 did not correlate with the immune activation processes reflected by the serum and phenotypic marker groups A-D. Correlations between serum and certain lymphoid phenotypic markers were generally stronger later in HIV-1 infection when CD4 levels were less than 500/mm3. This study provides information for selecting markers for investigating immune changes in HIV-1 infection and immune-related diseases. Many serum and lymphoid phenotypic markers reflect related aspects of immune dysregulation. However, some markers can indicate different aspects of disease.