Mouse thymic virus (MTLV). A mammalian herpesvirus cytolytic for CD4+ (L3T4+) T lymphocytes.

Mouse thymic virus (MTLV; ICTV designation murid herpesvirus 3) infects developing T lymphocytes of neonatal mice, causing thymic necrosis and acute immunosuppression. Infected animals shed virus indefinitely. In the present report, two-color flow cytometric analysis of T lymphocyte subpopulations defined by the markers CD4 (L3T4) and CD8 (Lyt-2) was used to determine whether MTLV was lytic for a specific thymocyte population. At peak necrosis (8-11 d after infection), numbers of CD4+8+ cells in the thymus were reduced by 80% or more as compared with controls, and CD4+8- cells were reduced by greater than 98%. The major survivors were CD4-8+ and CD4-8- lymphocytes. These data indicate that the CD4 bearing lymphocyte is a primary target for cytolysis during MTLV infection. Possible parallels between MTLV and a newly described lymphotropic human herpesvirus, human herpesvirus 6 (HHV-6/HBLV), are also suggested.

Advanced glycosylation endproducts on erythrocyte cell surface induce receptor-mediated phagocytosis by macrophages. A model for turnover of aging cells.

Glucose can react nonenzymatically with amino groups of proteins to form covalent Amadori products. With time these adducts undergo further rearrangements to form irreversible advanced glycosylation endproducts (AGE), which accumulate with protein age. A specific AGE, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI), has been identified on proteins in vivo. We have recently shown that a macrophage receptor specifically recognizes and internalizes proteins modified by AGE such as FFI, thus preferentially degrading senescent macromolecules. Reasoning that cellular turnover may be mediated by macrophage recognition of AGE-membrane proteins, we prepared human RBCs with FFI attached chemically. Human monocytes were incubated with either FFI-RBCs, IgG-opsonized RBCs, or PBS-treated RBCs. Erythrophagocytosis of FFI-RBCs was significantly higher than that of PBS-RBCs (55 vs. 4%; p less than 0.0025) and almost as high as that of IgG-RBCs (70%), and was competitively inhibited by AGE-BSA. AGE-RBCs were also prepared by incubating RBCs with various sugars. Human monocytes showed a 15% ingestion of glucose-RBCs, and a 26% ingestion of glucose-6-phosphate-RBCs, compared to 6% for PBS-RBCs. Similarly, diabetic mouse RBCs were phagocytosed by nearly three times more cells (21%) than normal mouse RBCs when exposed to syngeneic mouse macrophages. This phagocytosis was competitively inhibited (70%) by addition of excess AGE-BSA. The in vivo half-life of 51Cr-labeled mouse FFI-RBCs injected into syngeneic mice was reduced to 7 d, as compared to a half-life of 20 d for the controls. These data suggest that the macrophage receptor for the removal of glucose-modified proteins may also mediate the endocytosis of RBCs with AGE formed on their surface, and thus be responsible in part for the removal of some populations of aging cells.

Granulocyte/macrophage colony-stimulating factor is essential for the viability and function of cultured murine epidermal Langerhans cells.

A panning method has been developed to enrich Langerhans cells (LC) from murine epidermis. In standard culture media, the enriched populations progressively lose viability over a 3-d interval. When the cultures are supplemented with keratinocyte-conditioned medium, LC viability is improved and the cells increase in size and number of dendritic processes. Accessory function, as monitored by stimulating activity in the mixed lymphocyte reaction (MLR), increases at least 10-20-fold. The conditioned media of stimulated macrophages and T cells also support the viability and maturation of cultured LC. A panel of purified cytokines has been tested, and only granulocyte/macrophage colony-stimulating factor (GM-CSF) substitutes for bulk-conditioned medium. The recombinant molecule exhibits half-maximal activity at 5 pM. Without activity are: IL-1-4; IFN-alpha/beta/gamma; cachectin/TNF; M- and G-CSF. A rabbit anti-GM-CSF specifically neutralizes the capacity of keratinocyte-conditioned medium to generate active LC. However, GM-CSF is not required for LC function during the MLR itself. We conclude that the development of immunologically active LC in culture is mediated by GM-CSF. The observation that these dendritic cells do not respond to lineage-specific G- and M-CSFs suggests that LC represent a distinct myeloid differentiation pathway. Because GM-CSF can be made by nonimmune cells and can mediate the production of active dendritic cells, this cytokine provides a T-independent mechanism for enhancing the sensitization phase of cell-mediated immunity.

Macrophages phagocytose thymic lymphocytes with productively rearranged T cell receptor alpha and beta genes.

The thymus gland is important for the formation of competent T lymphocytes. However, there is long-standing evidence that greater than 95% of newly formed thymocytes do not emigrate to peripheral lymphoid tissues but instead die locally. We have identified a rapid and selective pathway for thymocyte turnover in vitro. The mechanism entails binding, uptake, and digestion by macrophages. The susceptible cells are a subpopulation of double-positive thymocytes. These thymocytes can be enriched by virtue of their high buoyant density in Percoll and prove to have low levels of surface CD3 and little or no surface TCR. However TCR-alpha and -beta genes have undergone rearrangement, and full length alpha and beta transcripts are abundant. Therefore many double-positive cells rearrange and express TCR genes but do not have normal levels of TCR on the cell surface. We propose that thymocytes that undergo high turnover in situ are unable to form receptors that can be selected by MHC molecules in the thymus, and that these cells are recognized and cleared by the macrophage.

A monoclonal antibody to a human neutrophil-specific plasma membrane antigen. Effect of the antibody on the C3bi-mediated adherence by neutrophils and expression of the antigen during myelopoiesis.

We have used mice selectively tolerized to antigens of human lymphocytes by treatment with cyclophosphamide to raise an mAb, BH2-C6, that reacts with a plasma membrane antigen specific for human neutrophils. This specificity is demonstrated by indirect immunofluorescence microscopy, cytochemical analysis of fluorescence-positive and -negative cell populations separated by flow cytometry, and by the selective, complement-mediated killing of mAb BH2-C6-treated neutrophils. Additional evidence for the neutrophil specificity of mAb BH2-C6 is shown by immunoelectron microscopy, which demonstrates a lack of reactivity with human eosinophils. Immunoblotting of SDS-PAGE-separated proteins of polymorphonuclear leukocytes with 125I-labeled BH2-C6 identifies protein with an average molecular mass of 157 kD. Binding studies show that, at saturation, neutrophils bind 214,000 molecules of 125I-BH2-C6 per cell. Addition of mAb BH2-C6 to neutrophils significantly reduces the number of C3bi-opsonized sheep erythrocytes (EIgMC3bi) bound by these cells. This reduction is partly reversed by the presence of soybean trypsin inhibitor (SBTI), indicating that at least one part of this inhibition is due to BH2-C6-stimulated secretion of a serine protease that may affect ligand binding. Cytochemical analysis of normal human bone marrow cells sorted by cytofluorimetry identifies the promyelocyte as the precursor cell that first expresses BH2-Ag on the plasma membrane. Using the leukemic cell line HL-60, we demonstrate that only inducers of granulocytic differentiation, cis-retinoic acid, and dimethyloxazolidine stimulate the expression of BH2-Ag. These results show that the expression of BH2-Ag during myelomonocytic differentiation is a property uniquely possessed by cells committed to the neutrophilic lineage.

Relative efficacy of human monocytes and dendritic cells as accessory cells for T cell replication.

Monocyte-specific monoclonal antibodies (7) were used to compare the efficacy of monocytes and dendritic cells as accessory or stimulator cells for human T cell replication. Both unfractionated and plastic-adherent mononuclear cells were first treated with a cytolytic antimonocyte antibody that kills greater than 95% of monocytes but not dendritic cells. When tested as stimulators of the mixed leukocyte reaction (MLR) and of oxidative mitogenesis (the proliferation of T cells modified with sodium periodate), the monocyte-depleted cells had normal or enhanced stimulatory capacity. Monocyte-depleted mononuclear cells also proliferated normally to soluble antigens (Candida albicans, tetanus toxoid), even under limiting conditions of cell dose, antigen dose, and culture time. Adherent blood mononuclear cells were next separated into monocyte-enriched and -depleted components using fluoresceinated antimonocyte antibody and the cell sorter. The depleted fraction (less than 2% monocytes by esterase staining and by cytology) contained the dendritic cells and exhibited at least 75% of the accessory activity. The monocyte-rich fraction (approximately 97% esterase positive) stimulated the MLR and oxidative mitogenesis weakly, and was comparable in potency to nonadherent cells. Cell-specific antibodies and complement were also used to prepare dendritic cells that were thoroughly depleted of monocytes and lymphocytes. The dendritic cells (70-80% pure) were potent stimulators of the allogeneic MLR, syngeneic MLR, and tetanus toxoid response, being active at stimulator to responder ratios of 1:100 or less. Taken together with previous studies (1, 2), these experiments indicate that the dendritic cell is the major stimulator of T cell replication in man. The contribution of class II products of the major histocompatibility complex (7) was then evaluated with a new monoclonal, 9.3F10. Accessory function was dramatically inhibited if cells bearing class II antigens were killed with 9.3F10 and complement, or if class II molecules were blocked by the addition of 9.3F10 Fab to the culture medium. The expression of 9.3F10 class II products was therefore studied on purified monocytes and dendritic cells. Most if not all cells in both populations reacted with 9.3F10, and each population exhibited approximately 150,000 125I-Fab 9.3F10 binding sites per cell. Since Ia+ dendritic cells are active accessory cells, but Ia+ monocytes are not, class II products are necessary but not sufficient for the stimulation of T cell proliferation in man.

Blockade of clearance of immune complexes by an anti-Fc gamma receptor monoclonal antibody.

Clearance of immune complexes by the mononuclear phagocyte system is important for maintaining normal host defenses against bacterial and viral assault (1), but also contributes to the pathogenesis of a variety of immune- mediated diseases . For example, removal from the circulation of IgG-coated erythrocytes and platelets by the MPS is the sine qua non of immune-mediated cytopenias (2, 3). On the other hand, abnormally decreased removal by the MPS of smaller, soluble immune complexes may play a role in the pathogenesis of immune complex-mediated tissue damage found in such autoimmune diseases as SLE (4). Although the physicochemical nature and the size of immune complexes can influence rates of clearance and sites of deposition (reviewed in 5), interactions between immune complexes and the MPS in vivo are poorly understood. The inability to directly measure binding or internalization of immune complexes by cells in the liver and spleen has made the analysis of the molecular basis of immune complex clearance very difficult . Receptors for the Fc portion of IgG (FcgammaR) and for complement (CR) undoubtedly play a role in the removal of immune complexes, but the relative importance of these receptors is not known.

Ontogeny of Fc receptors and complement receptor (CR3) during human myeloid differentiation.

Two different Fc receptors for IgG (Fc gamma R) have been identified on human leukocytes: a high avidity receptor (Fc gamma Rhi) present on monocytes but not on neutrophils, and a low avidity receptor (Fc gamma Rlo) present on neutrophils but not on monocytes. Fc gamma Rlo can be inhibited and the receptor precipitated by monoclonal antibody 3G8. We have used this monoclonal antibody to study the course of Fc gamma Rlo appearance on bone marrow cells, leukocytes of patients with chronic myelogenous leukemia (CML), and HL-60 and U937 cells induced to differentiate with agents such as dimethyl sulfoxide (DMSO), retinoic acid, phorbol myristate acetate, and lymphokine. We report that Fc gamma Rlo is a late differentiation antigen, first expressed at the metamyelocyte stage. Since precursors to metamyelocytes bear Fc gamma R, and the promyelocyte line HL-60 bears Fc gamma Rhi, there must be a progressive loss of Fc gamma Rhi during myeloid differentiation and the reciprocal expression of Fc gamma Rlo. Results of immunoprecipitation and polyacrylamide gel analysis of the proteins are consistent with these results. We have also studied the receptor for the C3bi complement component (CR3), which is blocked and immunoprecipitated by monoclonal antibody OKM10. During DMSO-driven differentiation of HL-60 cells, we find that CR3 is induced on all cells, whereas Fc gamma Rlo is induced on only 24% of cells, suggesting that CR3 appears earlier during differentiation than Fc gamma Rlo does.

Rate of replication of the murine immunoglobulin heavy-chain locus: evidence that the region is part of a single replicon.

We measured the temporal order of replication of EcoRI segments from the murine immunoglobulin heavy-chain constant region (IgCH) gene cluster, including the joining (J) and diversity (D) loci and encompassing approximately 300 kilobases. The relative concentrations of EcoRI segments in bromouracil-labeled DNA that replicated during selected intervals of the S phase in Friend virus-transformed murine erythroleukemia (MEL) cells were measured. From these results, we calculated the nuclear DNA content (C value; the haploid DNA content of a cell in the G1 phase of the cell cycle) at the time each segment replicated during the S phase. We observed that IgCH genes replicate in the following order: alpha, epsilon, gamma 2a, gamma 2b, gamma 1, gamma 3, delta, and mu, followed by the J and D segments. The C value at which each segment replicates increased as a linear function of its distance from C alpha. The average rate of DNA replication in the IgCH gene cluster was determined from these data to be 1.7 to 1.9 kilobases/min, similar to the rate measured for mammalian replicons by autoradiography and electron microscopy (for a review, see H. J. Edenberg and J. A. Huberman, Annu. Rev. Genet. 9:245-284, 1975, and R. G. Martin, Adv. Cancer Res. 34:1-55, 1981). Similar results were obtained with other murine non-B cell lines, including a fibroblast cell line (L60T) and a hepatoma cell line (Hepa 1.6). In contrast, we observed that IgCh segments in a B-cell plasmacytoma (MPC11) and two Abelson murine leukemia virus-transformed pre-B cell lines (22D6 and 300-19O) replicated as early as (300-19P) or earlier than (MPC11 and 22D6) C alpha in MEL cells. Unlike MEL cells, however, all of the IgCH segments in a given B cell line replicated at very similar times during the S phase, so that a temporal directionality in the replication of the IgCH gene cluster was not apparent from these data. These results provide evidence that in murine non-B cells the IgCH, J, and D loci are part of a single replicon.

Quantitation of surface antigens on cultured murine epidermal Langerhans cells: rapid and selective increase in the level of surface MHC products.

It was recently discovered that murine epidermal Langerhans cells (LC) changed significantly in function and phenotype when maintained in culture. Notably, accessory cell function for primary immune responses increased while cytologic markers like ATPase, nonspecific esterase, and Birbeck granules were lost. To further analyze LC differentiation, we used flow cytometry and a panel of 22 monoclonal antibodies to quantitate changes in surface antigens at the single-cell level. A striking change was a fivefold increase in the amount of Ia antigens (which are expressed on class II MHC products) during the first day of culture. The increase was evident within 3 h and reached a plateau at 15-24 h. Both I-A and I-E products behaved similarly. The increase in Ia was blocked by 1 microgram/ml cycloheximide. Expression of other surface antigens was then monitored on Ia+ LC by two-color flow cytometry. Low levels of class I (H-2D and H-2K) MHC products were detected on freshly isolated LC, and these antigens also increased severalfold during the first day of culture. Fc receptors (identified with the 2.4G2 mAb) and the F4/80 macrophage antigen decreased, as reported previously. Three antigens that were detected in fresh suspensions were expressed at constant levels in culture. These were the C3bi receptor and the pan leukocyte and interdigitating cell antigens. Several leukocyte antigens that were not found initially on LCs did not appear, including B220 anti-B cell, 33D1 anti-dendritic cell, and CD4, CD5, CD8 T-cell specificities. We conclude that the surface of cultured LCs undergoes selective changes in culture. As a result, the cells are rich in Ia and H-2 and have detectable C3bi receptors, but have little or no LFA-1, Ti, CD4, 5, and 8, 33D1, 2.4G2, F4/80, and B220 antigens.

Levels of soluble CD8 antigen and circulating immune complexes in intravenous drug abusers: relationships to HIV antibody serology.

A total of 36 intravenous drug abusers (IVDA) were studied for circulating immune complexes (CIC) and serum soluble CD8 antigen (sCD8). None had symptoms or signs of AIDS-related complex or AIDS. sCD8 levels were significantly higher in 18 patients who had HIV antibody (Ab) compared with 18 patients who were HIV Ab negative (1640 +/- 578 virus 804 +/- 264 U/ml, p less than 0.0001). In HIV Ab+ patients but not in HIV Ab- patients, sCD8 levels significantly correlated with percentages and absolute numbers of activated CD3+DR+ peripheral blood mononuclear cells (p = 0.0024 and 0.0183, respectively). Also in HIV Ab+ patients, CIC levels were significantly greater for both anti-C3 binding (13.1 +/- 11.1 versus 2.9 +/- 3.4 micrograms/ml, p = 0.002) and C1q binding (23.5 +/- 20.2 versus 6.3 +/- 4.3 micrograms/ml, p = 0.001) CIC. Serum C4 concentrations were lower in the HIV Ab+ patient group (33.9 +/- 10.1 versus 41.6 +/- 12.4 mg/dL, p = 0.043). In the seropositive group, IgG levels were higher (2206 +/- 859 versus 1615 +/- 645 mg/dl) and total CD4 cell counts were lower (757 +/- 344 versus 1172 +/- 402 cells per mm3), but at a less significant level (p = 0.024 and 0.005, respectively), than that seen for sCD8 and C1q CIC differences. These results suggest that elevations of both the lymphocyte activation marker sCD8 and antigen nonspecific CIC characterize earlier stages of HIV infection in IVDA.

Merocyanine 540 staining of human leukemic cells: relation to stage of disease.

Previous work based on fluorescence microscopic observation has indicated that leukemic leukocytes and immature hematopoietic precursor cells show a greater permeability to the membrane stain, merocyanine 540 (MC) than normal, mature cells and that changes in MC permeability seem to be correlated with failure in membrane maturation during leukemic cell differentiation. In the interest of addressing questions concerning the efficacy of the MC staining reaction as a diagnostic tool in clinical contexts relevant to leukemia, we have looked for any correlations which might exist between the MC staining patterns displayed by circulating leukocytes, cellular morphology and the clinical status of 53 patients with leukemia and non-Hodgkin's lymphoma, using fluorescence activated cell sorting. In 85% of cases, MC staining was found to be correlated with blood status while in 15% of the cases discrepancies were found. These results are discussed in light of changes in the hematologic profiles of the patients during the clinical course.

The cholinergic system of the primitive streak chick embryo.

The presence of neurotransmitters at stages of embryonic development prior to neurulation has been demonstrated in several systems. Although the functions of these molecules at early stages of embryogenesis have not been ascertained, it is possible that they are involved in aspects of cell migration, regulation of the synthesis of macromolecules, intercellular communication, and in the transmission of positional information during gastrulation. As an initial approach to the resolution of questions concerning the function of transmitters during early development, we have begun a study of the cholinergic system in the primitive streak chick embryo (Hamburger-Hamilton stages 3 + to 5). We have found that the chick embryo: (1) can use exogenously applied choline for the synthesis of acetylcholine; (2) possesses a true acetylcholinesterase, which is predominantly in the form of the 4-6s monomer; and (3) can take up exogenous choline through a sodium-dependent, high-affinity choline transport system. To date we do not have any evidence for the presence of nicotinic or muscarinic receptors at the primitive streak stage.

Plasminogen in the chick embryo. Transport and biosynthesis.

As part of a program to define potential roles for plasminogen activation during development, we have studied the metabolism of plasminogen in the chick embryo. Here we report that: 1) plasminogen is present in significant quantities in the yolk of fertile, unincubated eggs; 2) the zymogen can be translocated intact, from the yolk to the developing embryonic circulation; and 3) de novo synthesis of plasminogen occurs during the early phases of embryonic life. The combination of a reservoir of the zymogen in the yolk and protein biosynthesis thus ensures the availability of a substrate for enzymes which may participate in morphogenetic events occurring throughout embryonic life.

Production of plasminogen activator in cultures of superior cervical ganglia and isolated Schwann cells.

Plasminogen activator has been implicated in tissue remodeling and cell migration during embryogenesis. In the developing nervous system, these processes are evident in the migration of neurons, axonal extension, Schwann cell migration, and the ensheathment and myelination of nerves. We have studied the production of plasminogen activator in cultures of superior cervical ganglia under conditions in which both neurons and glia are present. We have found that a principal source of the enzyme in these cultures is the glial cells and that the enzyme could not be detected at the growing tips of neurites. Plasminogen activator is also produced by Schwann cells isolated from neonatal rat sciatic nerve. The production of the enzyme by these cells is stimulated 6- to 10-fold by cholera toxin. Isolated Schwann cells and glial cells in the ganglion explant cultures produce the tissue form of plasminogen activator, a form of the enzyme not often found in nonmalignant cells. Preliminary experiments suggest that neuronal-glial interactions may regulate enzyme production by Schwann cells.

Merocyanine 540 as a fluorescent probe of membranes: staining of electrically excitable cells.

With the exception of certain blood cells considered in the accompanying paper (Valinsky, Easton and Reich, 1978), merocyanine 540 (MC 540), a fluorescent membrane probe, selectively strains the membranes of a wide variety of electrically excitable cells, but not those of nonexcitable cells. This reaction is Ca2+-dependent when staining is performed in buffered iso-osmotic sucrose, Ca2+-independent when staining proceeds at high ionic strength, inhibited by La3+ and sodium Suramin, enhanced by controlled, low level photosensitization of cell-associated dye and essentially irreversible. These characteristics of the staining reaction depend upon the maintenance of both cell viability and a normal unperturbed membrane structure. Although the mechanisms involved in the staining specificity remain unknown, observation of MC 540 partitioning between benzene and water in model reactions indicates that dye transport into hydrophobic solvents is accompanied by the formation of stoichiometric complexes with cations and phospholipids. These results may suggest the existence of specific, possibly phospholipid-rich membrane domains that mediate complex formation with MC 540 in excitable cells; comparable domains either would not exist, or would be inaccessible at the external surfaces of nonexcitable cells.

Merocyanine 540 as a fluorescent probe of membranes: selective staining of leukemic and immature hemopoietic cells.

We have reported (Easton, Valinsky and Reich, 1978) that merocyanine 540 (MC 540) specifically stains a variety of living excitable cells, but not nonexcitable cells. This paper describes the exceptional permeability to MC 540 of leukemic leukocytes and immature hemopoietic precursor cells. We have used fluorescence microscopy and uptake of radioactive dye to study MC 540 staining of peripheral blood leukocytes from 80 leukemic and 34 normal individuals; leukemic leukocytes stain, whereas normal leukcytes do not. The leukocyte staining reaction differs from that previously described for excitable cells since it is independent of the ionic composition of the staining medium, kinetically complex, enhanced by light, enhanced by oxygen and essentially irreversible. Virtually all circulating nucleated cells from leukemic individuals are stained to approximately the same extent, and there is no qualitative or quantitative distinction between the various forms of leukemia. We have also found that MC 540 interacts with granulopoietic colony-forming cells (CFU-C) and with spleen colony-forming cells derived from mouse bone marrow (CFU-S). We cannot as yet identify a specific property of leukocyte plasma membranes that determines MC 540 permeability; since changes in MC 540 uptake appear to be correlated with cellular maturation during normal hemopoiesis, the retention of staining by leukemic cells, some of which appear morphologically normal, may indicate of failure in membrane maturation during leukemic blood cell development.

Plasminogen activator in the bursa of Fabricius: correlations with morphogenetic remodeling and cell migrations.

The association of controlled extracellular proteolysis, mediated by plasminogen activator, with embryonic tissue remodeling and cell migration was studied in the developing bursa of Fabriculus of quail and chick embryos. We found: that the specific activity of plasminogen activator in the bursa changes as a function of developmental age; that these changes are correlated temporally with the migration of hemopoietic cells into the bursal rudiment and with the period of extensive remodeling in the bursal epithelium; that the enzyme is distributed asymmetrically in the epithelial and mesenchymal compartments of the bursa. Chick and quail plasminogen activators can be distinguished by differences in their rates of electrophoretic migration. When interspecific grafts between quail and chick embryos were analyzed in this way, we observed that hemopoietic precursor cells produce plasminogen activator during their colonization of the bursa.

Production of plasminogen activator by migrating cephalic neural crest cells.

Neural crest cells migrate extensively during embryonic development and differentiate into a wide variety of cell types. Our working hypothesis is that during migration, embryonic cells secrete proteases which modify local microenvironments, thereby facilitating directed cellular movements. In this communication, we report studies on the migration of cephalic neural crest cells in the avian embryo. We demonstrate that these cells produce high levels of the serine protease, plasminogen activator (PA), at the time of their initial migration from the neural tube and during their migration to and colonization of the developing head and neck.

T cell immunophenotypes and DR antigen expression in intravenous drug users. Relationship to human immunodeficiency virus serology.

Thirty-six intravenous drug users were studied for peripheral blood mononuclear cell (PBMC) immunophenotypes and human immunodeficiency virus (HIV) serological profiles. This population has a high risk for developing HIV infection. Half (18/36) were HIV antibody (Ab) negative (-) and half were positive (+). Total T lymphocytes (CD3+ and CD2+) were not different between HIV Ab-negative and HIV-positive groups. Unactivated T(CD3+DR-) cells/mm3 were less (p = 0.003) in HIV Ab-positive patients (1,467 +/- 628) compared to HIV Ab-negative patients (2,190 +/- 695). T-helper (CD4+) cells/mm3 were also less in HIV Ab-positive patients (762 +/- 344 vs. 1,161 +/- 419, p = 0.005). The most significant difference was in activated T lymphocyte CD3+DR+) percentages where the mean was 9.6% in those HIV Ab-positive compared to 3.8% in seronegatives (p less than 0.001). Preliminary studies showed that in vitro naloxone treatment of PBMC had no effects on immunophenotypic expression except for CD3+DR+ lymphocytes, where a significant reduction was observed in the HIV Ab-positive group (p = 0.022) but not in the HIV ab-negative group. These findings suggest that in certain populations, activated T cells may be an early manifestation of HIV infection.