Human macromolecular insoluble cold globulin (MICG). I. T-cell origin of T-MICG and null cell origin of N-MICG.

Although surface immunoglobulin characterizes B cells in man, there are few surface markers that distinguish T cells. We have described a new protein synthesized in human T cells, termed T-MICG. This protein is a macromolecule of 225,000 daltons, is insoluble in the cold, and migrates as a beta-globulin on electrophoresis. Separation of human peripheral blood lymphocytes into T and B-cell populations by rosette sedimentation and anti-human-Fab columns clearly demonstrated the T-cell origin of the 225,000 dalton component. Furthermore, null cells were shown to synthesize a protein of 185,000 daltons, termed N-MICG, with physical properties similar to T-MICG, T-MICG and N-MICG were shown to be antigenically dissimilar, employing antiserum to each of these proteins. The present studies demonstrate two novel cell surface markers, T-MICG and N-MICG, which characterize T cells and null cells, respectively.

Chronic lymphocytic leukemia cells lack the 185,000-dalton macromolecular insoluble cold globulin present on normal B lymphocytes.

We have recently characterized two lymphocyte-associated membrane proteins which have been termed 225,000-dalton and 185,000-dalton macromolecular insoluble cold globulin (225-MICG and 185-MICG, respectively) to distinguish their major physicochemical properties. These proteins differ antigenically, structurally, and in their cellular distribution. T cells can be distinguished by the synthesis and presence in the plasma membrane of 225-MICG, Null cells by the appearance of 185-MICG, and B cells by the appearance of both 225- and 185-MICG. The characterization of these two proteins in the monoclonal B lymphocytes of chronic lymphocytic leukemia forms the basis of this report. Using immunofluorescent microscopy, we found only 225-MICG on the surface of chronic lymphocytic leukemia (CLL) cells in 15 patients, whereas control B cells from 20 individuals displayed both 225- and 185-MICG. When MICG proteins were isolated and compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, normal B cells showed two stained bands, corresponding to 225- and 185-MICG, whereas the CLL cells demonstrated only the 225-MICG band. Using labeled amino acid incorporation into cellular protein, normal B cells were shown to synthesize 225- and 185-MICG, whereas CLL cells synthesized only 225-MICG, as determined by immune or cold precipitation of labeled cell lysates. When labeled secretions from B cells and CLL cells were analyzed by immune precipitation, 225- and 185-MICG were secreted by B cells, whereas neither protein was secreted by CLL cells. When normal B cells and CLL cells were mixed, incubated, and lysed together, both 225- and 185-MICG were present, thus excluding proteolysis as a cause of the absence of 185-MICG in CLL. The lack of 185-MICG in CLL distinguishes leukemic cells from normal B lymphocytes. Furthermore, the absence of this normal cell surface protein in these leukemic cells suggests a role for 185-MICG in the malignant transformation of lymphocytes.

Lymphosarcoma cell leukemia and other non-Hodgkin's lymphomas in leukemic phase.

Lymphosarcoma cell leukemia has been used to refer to three related clinical syndromes. As originally described, it refers to the invasion of peripheral blood by poorly-differentiated lymphocytic lymphoma. Blood involvement occurs in 10 to 70 percent of patients with poorly-differentiated lymphocytic lymphoma, depending on the methods and criteria used to define leukemic phase, but it may have little impact on the clinical course of such patients. Second, lymphosarcoma cell leukemia can describe a variant of chronic lymphocytic leukemia, presenting clinically without lymphoma. Although not all hematologists recognize this as a distinct entity, others believe that such patients have a poorer prognosis than those with typical chronic lymphocytic leukemia. In the absence of a lymph node biopsy diagnostic of poorly-differentiated lymphocytic lymphoma, the diagnosis of lymphosarcoma cell leukemia should be reserved for cases demonstrating immunologic features of poorly-differentiated lymphocytic lymphoma, namely bright surface immunoglobulin immunofluorescence, normal capping, and low mouse red cell rosette formation. Finally, lymphosarcoma cell leukemia has been used to describe the invasion of blood by other types of lymphoma, including large cell, lymphoblastic, and Burkitt's lymphoma, although these are better designated as the particular lymphoma in leukemic phase. When abnormal cells appear in the blood samples of patients with lymphoma, acute myelogenous leukemia must also always be considered, particularly in patients who have received substantial prior chemotherapy or irradiation.

Mechanism of immunoglobulin A polymerization.

Employing mercaptoethylamine as a reducing agent, it was demonstrated by analytical ultracentrifugation and polyacrylamide gel electrophoresis that polymeric immunoglobulin A (IgA) was reduced to a 10 S dimer and 7 S monomer, and that dimer IgA was more resistant to reductive cleavage than the higher polymers. When dimer and monomer IgA were subjected to electrophoresis in polyacrylamide gels in 8 M urea or chromatographed on Bio-Gel P-200 equilibrated in 4 M guanidine HCl, there was no dissociations into H, L, or J chains, suggesting that the interchain disulfide bridges between H--H, L--H, and H--J were intact and that mercaptoethylamine produced selective cleavage of intersubunit bonds. Only the dimer, with a sedimentation coefficient of 10.2 S, released J chain upon reduction with dithiothreitol. Polymers of IgA were reduced with mercaptoethylamine and subsequently alkylated with [14C]-iodoacetamide and the dimer and monomer isolated. The results demonstrated that the isolated dimer contained 2 mol of [14C]labeled S carboxyamidomethylcysteine per mol of dimer, while the monomer contained 1 mol of --SH per mol of monomer. The labeled dimer was then completely reduced with dithiothreitol and alkylated with [14C]iodoacetamide and J chain isolated. It was shown that the J chain contained no 14C-labeled sulfhydryl groups, while the monomer contained 1 mol of --SH per mol of monomer. These results suggest that J chain is disulfide-bonded to only two of the subunits of polymeric IgA and that the remaining subunits in the higher polymers are disulfide-bonded one to the other. This is similar to the model previously suggested for 19 S immunoglobulin M (IgM). The sulfhydryl data also suggests that polymeric IgA may not be a covalently bonded circular structure as has been shown for IgM. However, no conclusions can be made from this study regarding the structure of pentameric IgA, since this species was present in very small amounts in our polymer preparation.

Treatment of Pneumocystis carinii pneumonia in patients with AIDS.

A 44-year-old man with acquired immunodeficiency syndrome (AIDS) and Pneumocystis carinii pneumonia (PCP) who suffered adverse effects from treatment with trimethoprim-sulfamethoxazole (TMP-SMX) and was then treated with pentamidine isethionate is described, and approved and investigational drugs used in the management of PCP in the AIDS patient are discussed. After taking TMP-SMX, 240 mg trimethoprim and 1200 mg sulfamethoxazole, four times a day orally for 10 days at home, the patient was hospitalized complaining of nausea, vomiting, diarrhea, and fever. Intravenous TMP-SMX was begun at a dosage of 18 mg/kg/day of trimethoprim. Four days later, his condition had deteriorated and he had elevations of liver enzymes and a decrease in white blood cell (WBC) count. TMP-SMX was discontinued and pentamidine isethionate was started at a dosage of 4 mg/kg/day i.v. His symptoms and fever subsided and his liver enzyme levels and WBC count improved. After nine days of pentamidine his WBC count decreased; pentamidine was suspected as the cause and discontinued; no further therapy was needed. PCP was the initial infection that established this patient's diagnosis of AIDS. The patient did not have exertional dyspnea and nonproductive cough, which are usually seen in AIDS patients with PCP. TMP-SMX 20 mg/kg/day, based on the trimethoprim content, is the usual initial treatment for PCP. Adverse effects of TMP-SMX develop more frequently in AIDS patients than in non-AIDS patients with PCP. The recommended dose of pentamidine isethionate for the treatment of PCP is 4 mg/kg/day, im. or i.v. A few studies have shown good response to aerosolized pentamidine. Trials of investigational agents have excluded patients with severely compromised respiratory status; eflornithine, dapsone in combination with trimethoprim, and trimetrexate have been used. Corticosteroids should be considered a last effort until additional data are available. TMP-SMX may be used to prevent recurrence of PCP or to prevent the initial occurrence of PCP in AIDS patients. Intravenous or aerosol doses of pentamidine may be effective as prophylaxis. Sulfadoxine-pyrimethamine tried as prophylaxis produced adverse reactions. Despite its higher incidence of serious adverse effects in the AIDS population, TMP-SMX is considered preferable to pentamidine for initial therapy. Pentamidine is preferred for patients with documented allergy to TMP-SMX or failure to respond to a five- to seven-day course of TMP-SMX.

A new protein: macromolecular insoluble could globulin (MICG) derived from mouse thymocytes.

A novel protein synthesized and isolated from mouse thymocytes is described. The protein can be separated from radiolabelled cell lysates by taking advantage of its insolubility in the cold. It is a macromolecule with a molecular weight of 225,000 daltons, migrates as a beta-globulin on electrophoresis and has unique antigenic determinents as shown by the production of a monospecific antiserum.

Defective interleukin-2 production and responsiveness by T cells in patients with chronic lymphocytic leukemia of B cell variety.

The present studies were designed to investigate the mechanism(s) of the defective T cell proliferative response to various stimuli in patients with B cell chronic lymphocytic leukemia B-CLL. In 14 patients with advanced B-CLL (stage III or IV) we found the T cell response in the autologous (auto) and allogeneic (allo) mixed lymphocyte reaction (MLR) to be 35.7% and 30% of the controls, respectively. Proliferation in the MLR depends upon the production of and response to interleukin 2 (IL 2), a T cell growth factor. IL 2 production in eight B-CLL patients was 22% of the control. The response to IL 2 was measured by the increase in the T cell proliferation in the MLR with the addition of IL 2. T cell proliferation in both the auto and allo MLR of CLL patients was significantly lower than in the controls after the addition of IL 2. The proliferative response of normal T cells to stimulation by CLL B cells was 50% of the control. This latter response was increased to control levels when cultures were supplemented with exogenous IL 2, suggesting that CLL B cells could stimulate IL 2 receptor generation in normal T cells in an allo MLR, but not IL 2 production. The presence of IL 2 receptors on activated T cells was directly determined using anti-Tac, a monoclonal antibody with specificity for the IL 2 receptor. Of the mitogen- or MLR-activated T cells in CLL patients, 6% and 10%, respectively, expressed Tac antigen, whereas identically stimulated control T cells were 60% and 47% Tac+, respectively. Our findings suggest that T cells in B-CLL are defective in their recognition of self or foreign major histocompatibility antigens as demonstrated by their impaired responsiveness in the MLR. Thus, these cells are unable to produce IL 2 or generate IL 2 receptors.

Adjuvant corticosteroid therapy for Pneumocystis carinii pneumonia in AIDS patients.

OBJECTIVE: To review published abstracts, case reports, and journal articles and evaluate data examining the use of systemic corticosteroids as adjuvant treatment for Pneumocystis carinii pneumonia (PCP) in patients with AIDS. DATA SOURCES: Computerized online databases, peer-reviewed journals from January 1986 through September 1991, and personal communication with a National Institutes of Health correspondent. STUDY SELECTION: The authors identified 13 reports pertinent to this review. By author consensus, five studies were selected for analysis based on sample size, controlled study design, and clinical outcome measures. Recommendations of an expert panel from the National Institutes of Health and the University of California also are discussed. DATA EXTRACTION: Data are presented based on the methodologic strength of the studies reviewed. Studies are assessed on sample size, inclusion criteria, comparative cohort populations, specific patient outcome measures, and statistical analysis. DATA SYNTHESIS: Results of the study analysis support the use of systemic corticosteroids as early adjunctive therapy for AIDS patients with moderate-to-severe PCP who have an initial arterial oxygen partial pressure of less than 70 mm Hg or an alveolar-arterial gradient greater than 35 mm Hg on room air. Improved outcomes included decreased mortality, respiratory failure, and deterioration of oxygenation. Data evaluated have shown that adjuvant corticosteroid therapy is most effective when initiated within 72 hours of beginning specific antipneumocystis therapy. A small, but sometimes significant, increased rate of infection in steroid-treated patients was noted. CONCLUSIONS: Based on the literature reviewed, early systemic adjuvant corticosteroid therapy can benefit patients with moderate-to-severe AIDS-related PCP. The steroid regimen used in the largest controlled trial and recommended by the expert panel is prednisone 40 mg bid (days 1-5), then 40 mg/d (days 6-10), then 20 mg/d (days 1-21).

Human macromolecular insoluble cold globulin (MICG). II. Immunologic definition of T cell and null cell MICG and the biologic effect of antiserum to MICG.

Thymus cell-derived macromolecular insoluble cold globulin (T-MICG) is a 225,000-dalton protein, selectively synthesized in human T cells. Null cell-derived macromolecular insoluble cold globulin (N-MICG) is a 185,000-dalton protein, synthesized in null cells, and antigenically distinct from T-MICG. Evidence to support these conclusions was provided by using isolated cell preparations that were radiolabeled, lysed in desoxycholate, and precipitated with monospecific antiserum to each component. These studies demonstrated that antiserum to T-MICG precipitated a 225,000 dalton protein from PBL and T cells, but not from B or null cells. Antiserum to N-MICG reacted with a 185,000 dalton protein present in PBL and null cells, but not with lysates from either T or B cells. The plasma membrane distribution of these proteins was shown by absorption of antiserum to T + N-MICG with either isolated T or null cells. Antibody-induced cytotoxicity and immunofluorescence confirmed the cell surface location of T and N-MICG. Divergent biologic effects of these antisera were also noted. Antiserum to T-MICG inhibited T cell rosette formation and the one-way mixed lymphocyte reaction, although anti-N-MICG antiserum had no such effect. The potential importance of these proteins is discussed.

Macromolecular insoluble cold globulin (MICG): a novel protein from mouse lymphocytes. III. Relationship to the mixed lymphocyte reaction and effect of anti-MICG antiserum in vivo.

In the present communication we have examined the relationship between the synthesis of macromolecular insoluble cold globulin (MICG) and the mixed lymphocyte reaction (MLR). In addition, we have studied in vivo the effect of antiserum to MICG on the antibody response to sheep red blood cells. The experiments indicate that MICG synthesis compared to either IgM or total protein is selectively stimulated in responder T cells exposed to allogeneic stimulator cells in the MLR. Furthermore, cytotoxicity studies utilizing anti-MICG antiserum demonstrated that T cells bearing MICG on their surface are an essential component of the responder cell population in the MLR. In vivo administration of antiserum to MICG significantly suppressed both the primary and secondary antibody response to sheep red blood cells. A possible mechanism for this suppression is discussed.

Macromolecular insoluble cold globulin (MICG): a novel protein from mouse lymphocytes. IV. Evidence for the plasma membrane distribution of MICG.

Macromolecular insoluble cold globulin is a glycoprotein synthesized predominantly by T lymphocytes in the mouse. The present report details experiments demonstrating the plasma membrane distribution of MICG on T lymphocytes. By utilizing immunofluorescent techniques it was shown that MICG was located in the external cell surface of 98% of thymic lymphocytes and 60% of splenic lymphocytes. Furthermore, in spleen cells, it was demonstrated that T cells and not B cells were surface MICG positive. Antibody to MICG was able to cap all of the immunofluorescent-positive (60%) spleen cells. In contrast, anti-MICG antibody did not induce cap formation on thymus cells. Only when dilute solutions of antibody were used did MICG cap on the thymus cells. Employing limited proteolysis of thymus and spleen cells MICG was shown to be regenerated on the surface of T cells with a half-life of 3.5 hr. The distribution and cell surface characteristics of MICG are discussed in terms of a "receptor-like" function for this protein.

Macromolecular insoluble cold globulin (MICG): a marker for embryonic prothymocytes in the mouse.

Adult thymocytes and peripheral T cells synthesize and insert a glycoprotein into their plasma membrane that is termed macromolecular insoluble cold globulin (MICG). This protein, in contrast to other T cell markers, was shown to be present in embryonic prothymocytes as soon as they appear in the thymic rudiment. Furthermore, some hematopoietic cells in the fetal liver were shown to contain MICG at a period in gestation before the completion of lymphocyte migration to the thymus. These results are discussed in terms of the requirements for embryonic cell migration.

Leukemic-like membrane properties acquired by B lymphocytes when depleted of 185,000-dalton macromolecular insoluble cold globulin.

Human peripheral blood lymphocytes can be phenotypically identified by the presence of one or both of two proteins, 225,000-dalton macromolecular insoluble cold globulin (225-MICG) and 185,000-dalton MICG (185-MICG). T cells synthesize and insert into their plasma membrane 225-MICG, null cells 185-MICG, and B cells both 225 and 185-MICG. In contrast, the monoclonal B cells of chronic lymphocytic leukemia are characterized by the presence of 225-MICG and the absence of 185-MICG. We have recently found it possible to chemically deplete 185-MICG from viable normal B cells by treating them with diisopropylfluorophosphate (DFP), thus making normal B cells phenotypically resemble leukemic cells. In the present report we determined whether certain peculiar properties of these leukemic cells would be associated with the normal B cells chemically depleted of 185-MICG. In normal B cells, SIg diffuses in the lipid bilayer to form clusters and caps under appropriate conditions, while in chronic lymphocytic leukemia (CLL) cells this does not occur. Normal B cells depleted of 185-MICG fail to undergo capping of SIg or surface MICG under appropriate conditions. Both DFP-treated B cells and CLL cells tend to rupture when smeared on a glass slide. Both CLL cells and DFP-treated B cells fail to secrete 225-MICG after it has been synthesized intracellularly. The relationship of these findings to the mechanisms of secretion and capping are discussed.

Identification of macromolecular insoluble cold globulin (MICG) as a new marker shared by NK and ADCC cells, but not expressed by NC cells.

We report here that cytotoxic pretreatment of spleen cells from six different strains of young adult mice with a monospecific rabbit antiserum against macromolecular insoluble cold globulin (MICG) effectively abrogates spontaneous NK activity directed towards YAC-1 tumour cells. MICG is a 225,000 molecular weight glycoprotein that is present in the plasma membrane of adult thymocytes and peripheral T cells, as well as in embryonic prothymocytes, but absent in granulocytes and B lymphocytes. The diminished NK activity in lymphocyte populations selectively depleted of MICG+ cells could not be restored by in vitro exposure to the NK boosting agents interleukin-2 (IL-2) and interferon. Lymphokine-activated spleen NK cells, generated by 48 hr preculture with IL-2 or interferon, expressed high levels of MICG surface antigen, moderate amounts of Thy 1.2 and, in striking contrast to spontaneous NK, very low to negligible amounts of AsGM1. Likewise, spontaneous NK cells in bone marrow were also shown to be both MICG+ and AsGM1+, while lymphokine-activated bone marrow NK cells remained MICG+, but lacked AsGM1. Thus, a clear distinction could be observed between spontaneous and activated NK cells with respect to differential expression of MICG and AsGM1. MICG was also detected on ADCC effector cells, whereas no surface MICG could be found on NC cells. These data are in line with the view that at least certain types of NK cells develop along a common lineage with T lymphocytes in the mouse.

T-cell abnormalities in inflammatory bowel disease are mediated by interleukin 2.

Inflammatory bowel disease (IBD) may be an immunologically mediated disorder in which T cells are unable to respond appropriately to cell surface-associated antigens. To test this possibility, 37 patients with IBD, 24 with Crohn's disease and 13 with ulcerative colitis who were not being treated with immunosuppressive therapy were studied. The ability of T cells to proliferate in response to autologous or allogeneic cells, i.e., the autologous or allogeneic mixed-lymphocyte reaction (MLR) was tested. The autologous MLR was depressed using patient cells compared to control cells, regardless of disease type or activity (1564 +/- 223 cpm versus 3300 +/- 381 cpm, P less than 0.05) while the allogeneic MLR was depressed in patients with active disease only (29,833 +/- 2871 cpm versus 46,799 +/- 3340 cpm, P less than 0.01). The ability of T cells to recognize and lyse allogeneic cells, allogeneic cell-mediated lympholysis (CML), was also low in patients with active disease (24 +/- 4% versus 37 +/- 3%, P less than 0.05). Since T-cell proliferation and cytotoxicity depend upon adequate production of and response to a T-cell growth factor, interleukin 2 (IL-2), IL-2 production and responsiveness in IBD were studied. IL-2 production by patient T cells in response to phytohemagglutinin was only 39% of control values, P less than 0.05. The response to IL-2 was measured by the increase in T-cell proliferation in the autologous MLR in medium alone or medium supplemented with IL-2. Control T-cell proliferation rose from 3300 +/- 381 cpm to 10,761 +/- 428 cpm with exogenous IL-2 (P less than 0.001). Patient T-cell proliferation rose from 1564 +/- 223 cpm to 6817 +/- 771 cpm with IL-2 (P less than 0.001) but did not reach the level of the IL-2-supplemented control autologous MLR (P less than 0.05). In addition, the percentage of activated patient T cells having Tac antigen (IL-2 receptor) was depressed (P less than 0.05). These findings did not vary with disease type or activity. It is concluded from these data that peripheral blood T lymphocytes from patients with IBD have a diminished response to cell surface antigens which is associated with a decrease in IL-2 production and receptor generation. These defects may be responsible for the depressed T-cell proliferation and cytotoxicity that accompany IBD.

Detection of human immunodeficiency virus type 1 provirus in mononuclear cells by in situ polymerase chain reaction.

BACKGROUND: Studies of human immunodeficiency virus type 1 (HIV-1) infection have attempted to quantitate the viral load correlate it with the degree of immune deficiency. In one study, only about 1 in 10,000 peripheral-blood mononuclear cells (PBMC) expressed HIV-1, but in other studies, at least 1 in 100 CD4-positive cells was infected and harbored the HIV-1 provirus. METHODS: We developed a new, highly sensitive in situ polymerase-chain-reaction (PCR) method that amplifies selected genetic regions within intact single cells. We used this technique to determine the proportion of PBMC carrying HIV-1 provirus in infected patients in different stages of disease. RESULTS: None of the PBMC from 11 HIV-1--seronegative patients were found to be positive for HIV-1 provirus by the in situ PCR method. In 56 patients infected with HIV-1, the percentage of PBMC with HIV-1 ranged from 0.1 percent to 13.5 percent. The mean percentage of infected mononuclear cells was greater in 13 patients with persistent generalized adenopathy (mean, 6.6 percent) and 19 with the acquired immunodeficiency syndrome (Stages IV-A to IV-C) (4.6 percent) than in 19 patients with asymptomatic HIV-1 infection (0.9 percent) (P less than 0.001). However, in five patients with Kaposi's sarcoma (Stage IV-D), an average of only 1.6 percent of mononuclear cells were infected. CONCLUSIONS: In HIV-1 infection, the proportion of PBMC that are infected appears to be at least 10 times higher than previously described. It is likely that most infected cells contain HIV-1 provirus in a latent or defective form that was not detected in some earlier studies.

Macromolecular insoluble cold globulin (MICG): a marker for pluripotential hemopoietic stem cells.

In embryonic mice pluripotential hemopoietic stem cells (PHSC) originate in the yolk sac and migrate to the fetal liver and from there to the bone marrow. Hemopoietic cells from yolk sac and fetal liver also migrate to the thymic primordium, and within the thymic environment these prothymocytes differentiate into mature T cells. We have recently demonstrated that macromolecular insoluble cold globulin (MICG), a T cell marker, is synthesized and inserted into the plasma membrane of embryonic prothymocytes as soon as these cells appear in the early thymus. In addition, we have shown that MICG+ cells are present within the fetal liver before the thymus has fully formed. In the present study we show that pluripotential hemopoietic stem cells in the fetal liver and bone marrow have MICG on their surface and represent a subpopulation of these MICG+ cells. The implications of these findings in relationship to stem cell differentiation and isolation are discussed.

Diminished interleukin 2 production and receptor generation characterize the acquired immunodeficiency syndrome.

The Acquired Immunodeficiency Syndrome (AIDS) is a disease found primarily in homosexual men, consisting of opportunistic infections and tumors, and is due to an acquired T-cell defect. In the present report, we studied various T-cell functions which might serve to distinguish homosexuals with a symptom complex including lymphadenopathy from those with AIDS. T lymphocytes from the lymphadenopathy and AIDS patients had markedly depressed proliferative responses in the autologous (auto) and allogeneic (allo) mixed lymphocyte reaction (MLR) compared to healthy homosexuals or heterosexual controls (P less than 0.001). Since proliferation in the MLR depends upon interleukin 2 (IL-2), a T-cell growth factor, we studied the production of and response to IL-2 in various groups of homosexuals and heterosexual controls. IL-2 production was markedly depressed in the lymphadenopathy and AIDS patients, 1.0 and 0.1 U/ml, respectively, compared to the healthy homosexual or heterosexual controls, both 5.0 U/ml (P less than 0.05 and P less than 0.01, respectively). Although the auto MLR of the lymphadenopathy patients rose to control values with the addition of exogenous IL-2, the auto MLR of the AIDS patients did not (P less than 0.01). This lack of responsiveness to IL-2 in the AIDS group was due to their inability to generate IL-2 receptors as shown by the absence of IL-2 absorption by activated cells and the absence of the Tac antigen (IL-2 receptor) on these same cells. The T4+ and T8+ T-cell subsets from the AIDS patients each demonstrated depressed IL-2 production and responsiveness following activation with autologous cells or mitogen, as well as the absence of Tac antigen. The diminished T-cell proliferation in the auto MLR in the lymphadenopathy group is associated with one defect, low IL-2 production, while the depressed proliferation in the AIDS group is associated with two defects, low IL-2 production and a lack of IL-2 receptor generation. These studies demonstrate that IL-2 receptor generation helps distinguish homosexuals with lymphadenopathy from those with AIDS, and that in addition to T-cell defects in the OKT4+ T-cell subset there are significant abnormalities in the OKT8+ T-cell subset in AIDS patients.

Ontogeny of interleukin 2 responsive cells in the fetal thymus.

The ontogeny of IL 2-responsive cells in the thymus of CBA/J mice was examined in neonatal animals and in fetuses at 14, 16, and 18 to 20 days gestation. The thymocytes were tested for responsiveness to 2 micrograms/ml Con A, TCGF, IL 2, and co-stimulation by Con A plus TCGF or IL 2. These responses were compared with those of thymocytes of 6- to 8-wk-old CBA/J. Thymocytes (1 X 10(5)) were cultured, and the reaction was measured at maximum response (96 hr). Neonatal animals gave an unusually high response to TCGF or partially purified IL 2 alone, approximately five times greater than the adult. A low but significantly enhanced proliferation, stimulated by partially purified IL 2 alone, was observed with 14-day fetal thymocytes, even though cultures of these cells in medium alone had higher background proliferation than any other age tested. In the co-stimulator reaction, proliferation significantly above background was measured at 16 days of gestation with Con A plus TCGF. The magnitude of the co-stimulator reaction increased with age, especially between the 16th and 18th day of gestation and immediately after birth.