Fc-receptors, Ia-antigens, and immunoglobulin on normal and activated mouse T lymphocytes

CD8 T cell memory recall is enhanced by novel direct interactions with CD4 T cells enabled by MHC class II transferred from APCs

Protection against many intracellular pathogens is provided by CD8 T cells, which are thought to need CD4 T cell help to develop into effective memory CD8 T cells. Because murine CD8 T cells do not transcribe MHC class II (MHC-II) genes, several models have proposed antigen presenting cells (APCs) as intermediaries required for CD4 T cells to deliver their help to CD8 T cells. Here, we demonstrate the presence of MHC-II molecules on activated murine CD8 T cells in vitro as well as in vivo. These MHC-II molecules are acquired via trogocytosis by CD8 T cells from their activating APCs, particularly CD11c positive dendritic cells (DCs). Transferred MHC-II molecules on activated murine CD8 T cells were functionally competent in stimulating specific indicator CD4 T cells. CD8 T cells that were “helped” in vitro and subsequently allowed to rest in vivo showed enhanced recall responses upon challenge compared to “helpless” CD8 T cells; in contrast, no differences were seen upon immediate challenge. These data indicate that direct CD8∶CD4 T cell interactions may significantly contribute to help for CD8 T cells. Furthermore, this mechanism may enable CD8 T cells to communicate with different subsets of interacting CD4 T cells that could modulate immune responses.

Receptor-mediated T cell absorption of antigen presenting cell-derived molecules

T cells tend to acquire a variety of cell surface molecules derived from antigen presenting cells (APCs). The molecule uptake occurs mainly during direct T/APC contact and is instigated by specific receptor/ligand interactions, such as T cell receptor (TCR) with a cognate peptide/MHC complex (pMHC) or CD28 with B7. The acquired molecules are targeted for internalization and degradation in the lysosome. Nevertheless, those molecules are expressed on the surface of T cells for a period of time. The presentation of APC-derived ligands by T cells exhibited a multitude of immunological effects via antigen-specific T/T interaction upon recognition of the absorbed antigens by contact with other T cells. Ligand uptake also occurs via absorption of membrane vesicles shed from APCs prior to contact (e.g., exosomes and plasma membrane-derived vesicles). As in ligand absorption via direct T/APC interaction, the absorption of pre-formed membrane vesicles is also dependent on specific receptor/ligand interactions. In this review, biological mechanisms underlying the ligand absorption process as well as the biological significance and application of the event will be discussed.

Ligand binding but undetected functional response of FcR after their capture by T cells via trogocytosis

Intercellular transfer of cell surface proteins by trogocytosis is common and could affect T cell responses. Yet, the role of trogocytosis in T cell function is still elusive, and it is unknown whether a molecule, once captured by T cells, harbors the same biological properties as in donor APC. In this study, we showed that FcgammaR as well as the associated FcRgamma subunit could be detected at high levels on murine and human T cells after their intercellular transfer from FcgammaR-expressing APC. Capture of FcgammaR occurred during coculture of T cells with FcgammaR-expressing APC upon Ab- or Ag-mediated T cell stimulation. Once captured by T cells, FcgammaR were expressed in a conformation compatible with physiological function and conferred upon T cells the ability to bind immune complexes and to provision B cells with this source of Ag. However, we were unable to detect downstream signal or signaling-dependent function following the stimulation of FcgammaR captured by T cells, and biochemical studies suggested the improper integration of FcgammaR in the recipient T cell membrane. Thus, our study demonstrates that T cells capture FcgammaR that can efficiently exert ligand-binding activity, which, per se, could have functional consequences in T cell-B cell cooperation.

T cell-mediated antigen presentation: a potential mechanism of infectious tolerance

Differentiation of the T cell repertoire and the physiology of T cell-mediated antigen presentation are reviewed in relation to mechanisms of self-tolerance. Recent research has indicated that T cell development is a continual process that optimizes partial recognition of self as a homeostatic set-point. Specific T cell antigen recognition of partial agonists is intrinsically linked to expression of class II MHC glycoproteins on T cells. Even ligands that act as TCR antagonists in IL-2 production assays have sufficient agonistic strength to induce expression of class II MHC glycoproteins on T cells. Thus, the intrinsic self-reactivity of the T cell repertoire may promote T-APC activity in vivo and may explain why thymic and peripheral T cells express low but significant levels of class II MHC glycoproteins. T-APC activity induces extensive apoptosis among responder T cells, causes desensitization among surviving responders, and has been implicated in the adoptive transfer of tolerance in the Lewis rat model of experimental autoimmune encephalomyelitis. Overall, these findings support a relationship between the partial recognition of self MHC ligands, expression of class II MHC glycoproteins on mature peripheral T cells, tolerogenic T cell-mediated antigen presentation, and desensitization of pathogenic self-reactive T cells.

Class II MHC/Peptide Complexes Are Released from APC and Are Acquired by T Cell Responders During Specific Antigen Recognition

T cell expression of class II MHC/peptide complexes may be important for maintenance of peripheral self-tolerance, but mechanisms underlying the genesis of class II MHC glycoproteins on T cells are not well resolved. T cell APC (T-APC) used herein were transformed IL-2-dependent clones that constitutively synthesized class II MHC glycoproteins. When pulsed with myelin basic protein (MBP) and injected into Lewis rats, these T-APC reduced the severity of experimental autoimmune encephalomyelitis, whereas unpulsed T-APC were without activity. Normal MBP-reactive clones cultured without APC did not express class II MHC even when activated with mitogens and exposed to IFN-γ. However, during a 4-h culture with T-APC or macrophage APC, recognition of MBP or mitogenic activation of responder T cells elicited high levels of I-A and I-E expression on responders. Acquisition of class II MHC glycoproteins by responders was resistant to the protein synthesis inhibitor cycloheximide, coincided with transfer of a PKH26 lipophilic dye from APC to responders, and resulted in the expression of syngeneic and allogeneic MHC glycoproteins on responders. Unlike rested I-A− T cell clones, rat thymic and splenic T cells expressed readily detectable levels of class II MHC glycoproteins. When preactivated with mitogens, naive T cells acquired APC-derived MHC class II molecules and other membrane-associated proteins when cultured with xenogeneic APC in the absence of Ag. In conclusion, this study provides evidence that APC donate membrane-bound peptide/MHC complexes to Ag-specific T cell responders by a mechanism associated with the induction of tolerance.

Major histocompatibility complex-based suppression: a mechanism for T-cell control

The crucial cell for immune system control is the T-cell. Current theories for T-cell control lack a credible mechanism for active down-regulation, because any mechanism that actively switches off T-cells must be secure from duplication by invading organisms. This hypothesis presents a system for T-cell control which is secure because it requires recognition of the highly polymorphic molecules of the MHC by the T-cell receptor as the down-regulatory mechanism, thus using the MHC as a form of individual security code.

Activation-dependent expression of low affinity IgG receptors Fc gamma RII(CD32) and Fc gamma RIII(CD16) in subpopulations of human T lymphocytes

Receptors for IgG (Fc gamma R) are expressed by small subpopulations of peripheral blood T lymphocytes. Our studies demonstrate that T lymphocytes can be induced in vitro to express two different low-affinity Fc gamma R. Mitogen activation of peripheral blood T lymphocytes obtained from eight healthy individuals leads to considerable augmentation of the Fc gamma RIII+ (CD32) T cell subpopulation. The highest percentage of CD32 expressing T lymphocytes could be detected after three days of activation. The T cell subpopulation which transiently express the CD32 antigen, encompasses CD4+ and CD8+ cells. Molecular cloning of the CD32 antigen by reverse transcription and polymerase chain reaction demonstrates that activated human T lymphocytes express the Fc gamma RIIIb2 isoform. The percentage of the Fc gamma RIII+ (CD16) T cell subpopulation was significantly increased only in the lymphocyte populations obtained from three out of eight volunteers immediately after mitogen activation. However, during short-term cell culture the CD16 expressing CD8+ T cell subset increased in the T cell population from all individuals investigated. During this time, the IL-2 receptor alpha-chain (CD25) expression level decreased as a function of time. In contrast to the CD8+CD16+ T cells, the percentage of the non-MCH-restricted CD56+CD16+ T cells was not influenced by mitogen activation and time of cell cultivation. We could show that CD16 in T cells is able to mediate a stimulus leading to proliferation of the CD8+CD56-CD16+ T cells but not that of the CD56+CD16+ T cell subset. This discrepancy cannot be explained by the expression of different Fc gamma RIII isoforms, because both T cell subsets express Fc gamma RIIIA alpha, as we demonstrate in this report.

Distribution of MHC class II antigens in feline tissues and peripheral blood

A new monoclonal antibody raised against gradient-purified feline immunodeficiency virus was found to recognize a bimolecular complex, comprising 27-29 kD and 32-35 kD subunits, on feline peripheral blood lymphocytes. Immunoperoxidase staining of feline tissues with this antibody, designated 43.2H2, demonstrated a reactivity pattern similar to that described for MHC II antigens of the dog, horse, and pig, but differed from human and mouse in having staining of T-cell zones in spleen and lymph nodes. Flow cytometric analysis revealed that 42.3H2 reacted with 88.97% +/- 16.00% of feline peripheral blood lymphocytes (n = 20). This high level of reactivity was found to be consistent by repeated sampling over a 4-month period. Two-color flow cytometric analysis was used to determined the reactivity pattern on lymphocyte subsets: 88.92% +/- 7.30% of CD4+ lymphocytes were 42.3H2-positive, while 85.99% +/- 11.46% of CD8+ cells were positive (n = 11 for both). B lymphocytes had the highest reactivity (99.47% +/- 0.45; n = 9) and also had the highest fluorescence intensity. By gating based on light scatter properties, 95.06% +/- 7.35% of monocytes were 42.3H2-reactive (n = 18), while granulocytes were negative.

Development and characterization of a monoclonal antibody to class II MHC antigens in rhesus macaques

The characterization of a monoclonal antibody with specificity for a monomorphic determinant on rhesus macaque class II antigens is described. This antibody, designated 2D16, is an IgG2b immunoglobulin which also displayed useful cross-reactivity with lymphoreticular cells and cell lines of other species including man, bonnet and stumptail macaques, sheep, dog and horse. Limited polymorphism of the 2D16 epitope was observed in the dog.

Cloned human T cells synthesize Ia molecules and can function as antigen presenting cells

TNP-specific proliferative cloned human T cell lines were investigated for their synthesis and cell surface expression of HLA-DR molecules and for their capacity to function as antigen presenting cells. Utilizing radioactive amino acid precursors for metabolic labeling, these studies demonstrated endogenous synthesis of HLA-DR molecules by cloned T cells, which by two-dimensional gel electrophoresis were similar to HLA-DR molecules expressed by B cells and monocytes. Moreover, when TNP-modified, the irradiated cloned T cells functioned very effectively to stimulate TNP-specific proliferation by cloned responders; when unmodified they were potent stimulators of allogeneic mixed leukocyte responses. Thus, for haptens covalently attached to cell membrane proteins and for allogeneic HLA antigens, Ia+ cloned T cells can function as effectively for antigen presentation and T cell activation as other Ia+ populations to which such properties have been ascribed.

Effect of infections with swine fever virus on immune functions. II. Lymphocyte response to mitogens and enumeration of lymphocyte subpopulations

Peripheral blood and spleen lymphocytes from pigs infected with a low-virulent strain of swine fever virus (SFV) were transiently hyporesponsive to the mitogenic action of PHA, PWM and Con A. The mitogenic reactivity of lymphocytes from lymph nodes from such pigs appeared to be enhanced rather than depressed at that time. In addition, hyper-responsiveness of peripheral blood lymphocytes (PBL) to these mitogens occurred in some pigs. PBL from pigs lethally infected with virulent SFV showed a persistent depression of the response to these mitogens, whereas lymphocytes from lymph nodes had a high responding capacity. A lymphocyte response to SFV antigens could not be demonstrated in infected pigs. These SFV infections did not markedly affect the percentage of lymphocytes in the blood and most lymphoid organs rosetting with sheep red blood cells. On the other hand, surface immunoglobulin-bearing lymphocytes were markedly increased in lymph nodes from pigs exposed to virulent SFV. The sum of both lymphocyte subpopulations in the lymph nodes from these pigs often considerably exceeded the 100% value, which strongly suggests the presence of cells bearing both surface immunoglobulin and receptors for dextran-treated sheep red blood cells. Possible correlations between these findings are discussed. The results suggest that infections with SFV induce systemic alterations in the process of lymphocyte recirculation in the pig.

Detection of Fc receptors

There are an almost bewildering array of assays one can use to detect Fc-receptors, but we have focused, for the most part, on relatively rapid and convenient methods--those that have become standard, e.g., EA rosetting procedures or uptake of soluble antigen-antibody complexes. For most types of Fc-receptor studies these methods are quite adequate. We have also tried to stress the newer methodology of detecting Fc receptors, i.e., the use of anti Fc-receptor antibodies, including monoclonal antibodies. The advent of monoclonal antibody technology, described in detail by Galfrè and Milstein, is changing the approach of many immunological procedures, and detection of Fc receptors is no exception. There are, it should be noted, many newer Fc-receptor methods, e.g., a solid-phase radioimmunoassay and a quantitative fluorometric assay, and methods such as these may be the most appropriate ones to choose in a particular experimental situation. In addition, we have not stressed "functional" Fc-receptor detecting assays, for example, antibody-dependent cell-mediated cytotoxicity (ADCC), which can be used to monitor the activity of Fc receptors in a whole cell population, rather than in single cells.

Antigen-binding receptors on T cells from long-term MLR. evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (VH) determinants strongly inhibited vesicle binding by both primary and long-term MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesicle-binding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectivelly blocked with the anti-VH reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.

Mast cell membrane antigens and Fc receptors in anaphylaxis. I. Products of the major histocompatibility complex involved in alloantibody-induced mast cell activation

Mast cell membrane antigens, coded by the K, I and D regions of the major histocompatibility complex of the mouse, were investigated for their presence at the cell surface and their participation in alloantibody-induced anaphylactic degranulation (DAAD). Anti-H-2 K, as well as anti-H-2 D antibodies were found to elicit DAAD. Recognition, on the mast cell membrane, of any product of the K or the D regions, either as the whole molecule, or as public or private antigens only, or even as a single private specificity, enabled alloimmune sera to trigger mast cell degranulation. By contrast, anti-Ia antibodies failed to elicit DAAD. By the autoradiographic technique, peritoneal mast cells were found to constitute a single homogeneous population, bearing H-2 D-coded antigens, although in smaller amounts than other peritoneal cells, but no Ia antigens or, if any, in much smaller amounts than other peritoneal cell type. These findings bring new evidence that mast cell alloantigens do participate in anaphylactic alloantibody-induced mast cell degranulation, by allowing bridging of (one?) Fc receptor with H-2 molecules.

Regulatory mechanisms in cell-mediated immune responses. VIII. Differential expression of I-region determinants by suppressor cells and their targets in suppression of mixed leukocyte reactions

The phenotypic expression of I-region determinants on cells producing and responding to MLR suppressor factor (MLR-TsF) was established in these studies. Alloantigen-activated MLR suppressor T cells (MLR-Ts), which produce MLR-TsF bearing gene products of the I-C subregion, were exposed to anti-I subregion sera and complement (C) before in vitro culture for MLR-TsF production. Suppressor activity was prevented by removal of cells bearing I-C determinants, whereas elimination of cells expressing I-A/B determinants had no effect. Interestingly, cytotoxic elimination of cells displaying I-J determinants also prevented MLR-TsF production. Admixture of anti-I-J and I-C antiserum-treated cells for MLR-TsF production failed to reconstitute suppressor activity, indicating that I-C and I-J gene products are expressed on a single population of cells critical to MLR suppression, rather than on distinct interacting subpopulations. Anti-I-C serum activity specific for I-C+ MLR-Ts was removed by adsorption with nylon wool-nonadherent splenic T cells and concanavalin A-activated thymocytes; adsorption with splenic B cells from anti-Thy-1,2 serum and C-treated spleen failed to remove relevant anti-I-C activity. These data suggest that regulatory I-C molecules, like I-J molecules, are preferentially expressed on T lymphocytes. Expression of I-C, or other I-region molecules on responder cell targets of MLR-TsF activity was also investigated. Responder cells were pretreated with anti-I subregion-specific sera in blocking or complement-dependent cytotoxic protocols before addition to MLR with MLR-TsF. Neither blocking nor the cytotoxic removal of cells bearing I-C or other I-region determinants from MLR responder populations interfered with MLR-TsF suppression. Because it has previously been demonstrated that MLR-TsF interacts optimally with activated, I-C syngeneic target cells, blocking and cytotoxic studies with anti-I subregion sera were also performed with responder cells activated by 24 h culture in MLR in the absence of MLR-TsF. Brief MLR-TsF pulse after antiserum treatment generated marked suppression regardless of blocking or absence of cells bearing serologically detected I-region determinants. I-C restricted suppression may thus be mediated not by interaction with I-C-bearing cells, but by target cells which exist in requisite association with populations of I-C+ cells.

Inflammatory and immune processes in the human lung in health and disease: evaluation by bronchoalveolar lavage

Bronchoalveolar lavage is an invaluable means of accurately evaluating the inflammatory and immune processes of the human lung. Although lavage recovers only those cells and proteins present on the epithelial surface of the lower respiratory tract, comparison with open lung biopsies shows that these constituents are representative of the inflammatory and immune systems of the alveolar structures. With the use of these techniques, sufficient materials are obtained from normal individuals to allow characterization of not only the types of cells and proteins present but their functions as well. Such observations have been useful in defining the inflammatory and immune capabilities of the normal lung and provide a basis for the study of lung disease. Lavage methods have been used to characterize inflammatory and immune processes of the lower respiratory tract in destructive, infectious, neoplastic, and interstitial disorders. From the data already acquired, it is apparent that bronchoalveolar lavage will yield major insights into the pathogenesis, staging, and therapy decisions involved in these disorders. (Am J Pathol 97:149--206, 1979).

Alloantigens derived from stimulator cells and bound onto MLC-activated rat T lymphoblasts

Rat T lymphocytes were activated in MLC (mixed leucocyte culture) against allogeneic stimulator cells. A few percent of such T blasts could be shown to carry IgM on their surface when a mixture of T and B lymphocytes was used as responder cells. The immunoglobulin was absent when purified T lymphocytes served as responders. A large proportion of MLC T lymphoblasts could be shown to carry stimulator alloantigens on their surface. These antigens were demonstrated (a) by indirect immunofluorescence using anti-stimulator alloantibody and FITC (fluorescein isothiocyanate Isomer I)-labelled F(ab)2 fragments of rabbit anti-rat Ig; (b) by autoradiography after internal labelling of stimulator cells, which showed the transfer of label from stimulator to responder cells. For biochemical analysis T blasts were restimulated with internally labelled allogeneic or syngeneic stimulator cells, and bound radiolabelled stimulator alloantigens were analysed on SDS-PAGE (sodium lauryl sulphate polyacrylamide gel electrophoresis). The results suggest that intact SD antigens with a molecular weight of 45,000 daltons and LD determinants with a molecular weight of 34,000 daltons derived from stimulator cells are found on MLC T blasts. No evidence of binding of the 27,000-dalton Ia chain to T blasts was found. Possible arrangements of these molecules on the responder blasts is discussed.

The characterization and functional significance of plasma membrane Fc Receptors

The importance of various components of the plasma membrane in the generation of the immune response has long been recognized. The identification and characterization of functional membrane receptors are essential for an understanding of the molecular basis of the immune response. The Fc receptor can be operationally defined as a site on the plasma membrane which is capable of binding the Fc portion of IgG. The Fc receptor has been reported on both lymphoid and nonlymphoid cell types. The functional significance of the receptor on these cell populations, as well as the biochemistry of the receptor, is not well established and is currently an important area of investigation. In this review, the Fc receptor will be discussed, primarily in human and murine lymphoid and macrophage cell populations, as a model of membrane immunoreceptors. The review will be divided into four sections. In the first section, consideration will be given to the binding assays used to study Fc receptor-ligand interactions and the class and subclass specificity of the receptor. The possibility of receptor-receptor interaction and quantitation of receptor sites will be discussed. The second phase of the review will be concerned with the fractionation and biochemistry of this receptor system, emphasizing the differences reported in receptor composition from different cell sources. In the third section of the review, the biologic significance of the receptor will be examined. The importance of the Fc receptor in opsonization and phagocytosis by mononuclear phagogytes, B-cell activation, antibody-dependent cell cytotoxicity, and the possible relationship of Fc receptors to the histocompatibility-linked immune response genes will be discussed. Finally, in the fourth section, the possible mechanisms of receptor regulation will be considered. Cell fusion experiments which have been performed and the expression of receptor activity on the hybrid cell clones will be discussed. Receptor regulation at the physiologic level will include the effects of cyclic nucleotide levels and cell cycle on receptor expression. It is the intent of this review to provide a detailed analysis of the Fc receptor and to emphasize its importance in microbiology, cell biology, and immunology.

Impairment of cell-mediated immunity functions by dietary zinc deficiency in mice

Several immunologic features were analyzed in mice on a zinc-deficient diet [Zn(-)], in mice pair-fed a diet containing zinc [Zn(+)], in mice fed a Zn(+) diet ad lib, and in mice fed laboratory chow ad lib. When placed on a Zn(-) diet, 6- to 8-week-old A/Jax, C57BL/Ks, and CBA/H mice showed loss of body weight, low lymphoid tissue weight, and profound involution of the thymus within 4-8 weeks after initiation of the regimen. Approximately 50% of the mice on the Zn(-) diet developed severe acrodermatitis enteropathica (lesions on tail and paws) and diarrhea. Pair-fed mice on the Zn(+) diet did not show any of these symptoms. Mice on the Zn(-) diet showed the following immune deficiencies: (i) depressed plaque-forming cells against sheep erythrocytes after in vivo immunization; (ii) depressed T killer cell activity against EL-4 tumor cells after in vivo immunization; and (iii) low natural killer cell activity. However, antibody-dependent cell-mediated cytotoxicity against chicken erythrocytes was normal in the mice on the Zn(-) diet. Deficiency of T killer cell activity was not observed when immunization with EL-4 allogeneic lymphoma cells was carried out in vitro. Progressive loss of relative and absolute number of Thy 1.2+ cells and a proportionate relative increase in cells bearing Fc receptors was seen in spleen and lymph nodes of Zn(-) animals. It appears that zinc is an essential element for maintenance of normal T cell and other immune functions in vivo.

Quantitative comparison of K cell potential in human T and null cells

Using a short-term quantitative assay of the antibody-dependent cell-mediated cytotoxicity (ADCC) of human peripheral blood lymphocytes towards 51Cr-labeled mouse lymphoma cells, it is possible to estimate the relative involvement of various lymphocyte populations in the overall ADCC potential displayed by unfractioned lymphocytes. Lymphocytes were separated by means of an anti-F(ab')2 column combined with sedimentation of E rosette-forming cells or EA rosette-forming cells, and a discontinuous serum albumin gradient, and were characterized by several surface markers. ADCC results were expressed as the cytotoxic capacity of 10(6) cells of each population (lytic units/10(6) cells) as well as the cytotoxic potential of each population by taking into account their relative numerical sizes. Although the null cells had the highest cytotoxic capacity, highly purified T cells also disclosed a cytotoxic capacity which, because of the large numerical excess of T cells over null cells, could account for closely equivalent cytotoxic potentials of these two populations. ADCC was entirely abolished by further removal of Fc receptor-bearing-cells, in all the subsets studied. Our data underline the role that the small proportion of Fc receptor-carrying T cells might play in ADCC.

T-cell-specific murine Ia antigens: serology of I-J and I-E subregion specificities

(B10 X B10.D2)F1 mice were immunized with B10.A(5R) concanavalin A-stimulated thymocyte blasts. The genetic disparity between donor and recipient was restricted to the I-J and I-E subregions of the murine major histocompatibility (H-2) complex. A high-titered, T-cell-specific anti I-JkEk serum was obtained. The antiserum lysed 27-30% of haplotype k, q, or s lymph node cells, 5.3 +/- 2% of haplotype k spleen cells, and did not lyse thymocytes. Nylon wool-passed lymph node or spleen cells (H-2k) showed considerable reactivity with anti-I-JkEk serum (35-40% lysis); anti-Thy1.2 plus complement-treated spleen cells did not react (less than 5% lysis). I-Ek antibody was detected by B10.A(3R) lymph node cell reactivity (20% lysis), whereas reaction with H-2k lymph node cells after B10.A(3R) absorption demonstrated IJk antibody (12% lysis). Lymphocyte activation with alloantigen or mitogen led to increased anti-I-JkEk serum reactivity. These results, showing antibody production to at least two T-cell Ia antigenic determinants by concanavalin A thmocyte blast immunization, suggest that a group of I-region-encoded T-cell specificities may not have been detected using conventional immunization protocols because they would not have comprised a major antigenic component of the immunizing cell population. The existence of multiple Ia antigenic determinants unique to T lymphocytes would have important implications for serological and functional studies of T-cell subpopulations.

A simple and convenient method for producing anti-activated lymphocyte alloantisera which does not require prior absorption

A BALB/c B cell lymphoma, 2PK-3, was found to be activation lymphocyte alloantigen (Ala-1)-positive by virtue of its ability to absorb out the cytotoxic anti-Ala-1.1-like antibody activity of an antiserum against activated BALB/c (Ala-1.1) lymphocytes. Injection of 2PK-3 cells from the spleens or ascites of lymphomatous BALB/c mice into H-2d compatible DBA/2 mice led to the rapid development of an antiserum with properties identical to anti-Ala-1.1 alloantisera. Thus, it did not significantly kill normal spleen cells from any one of 7 different strains tested, but killed over 85% of Con A- or LPS-stimulated spleen cells of 4 Ala-1.1 positive strains; activated lymphocytes of Ala-1.2 were not affected. Furthermore, these properties were seen with unabsorbed antisera. The results indicate that the Ala-1 phenotype may, in some cases, be retained on neoplastic lymphocytes and that such cells, being rapidly and easily obtained in vivo in large quantities, can serve as a convenient source of immunogen for the development of anti-Ala-1 alloantisera in certain donor-recipient combinations.

Sequential changes in T and B lymphocyte responses to Herpes simplex virus in man

Lymphocytes of seven patients with primary herpetic infection, twenty-three patients with recurrent herpes labialis and of nineteen control subjects were separated into T and B enriched cells by the use of nylon wool columns. In the absence of a herpetic infection the thymidine incorporation and macrophage migration inhibition responses to herpes simplex virus (HSV), Candida albicans and PPD, and the thymidine incorporation induced by PHA were functions of T cells. When a herpetic infection was present, the unfractionated lymphocyte response to HSV was increased, as measured by thymidine incorporation, but the T cell response was unchanged. However, T cells did show an increased response to HSV when prepared by elimination of cells forming rosettes with zymosan-complement. T cells of some patients were stimulated by contact with zymosan, and this correlated with the response to C. albicans. It is suggested that lymphocyte responses to HSV in man are mediated by T cells, but that these cells are specifically retained by nylon wool columns at the time of a herpetic infection. This may be associated with acquisition of an Fc receptor by the sensitized T cells.

Analysis of established human carcinoma cell lines for lymphoreticular-associated membrane receptors

Thirty-one different long-term established human carcinoma culture cell lines were examined for the presence or absence of receptors for the Fc portion of immunoglobulin G (IgG) ("Fc receptors"), the third component of complement (C3 receptors), sheep erythrocytes and mouse erythrocytes. Included in the catalogue of lines tested were adenocarcinoma of the adrenal cortex, colon, rectum, lung, liver, breast and kidney, and carcinomas of the uterine cervix, bladder and vulva. All lines were found to be consistently Fc receptor-negative, as assayed by rosette formation with sheep erythrocytes coated with subhemagglutinating amounts of anti-sheep erythrocyte antibodies, or bovine erythrocytes heavily coated with non-hemagglutinating anti-bovine erythrocyte antibodies. This is similar to results obtained with murine tumors: carcinomas are consistently Fc receptor-negative, while those lines which are Fc receptor-positive are invariably lymphoreticular in nature. The human carcinoma cell lines were also negative for complement (C3) receptors and spontaneous T and B rosette markers. It is proposed that, in most cases, rosette-forming cells found in primary human carcinomas are, as in the mouse or rat, representative of infiltrating non-malignant lymphoreticular cells.

Selective accumulation of cells with 'B' properties in stimulated lymph nodes

Draining lymph nodes from mice which had been stimulated with bacterial adjuvants or the skin sensitizing agent, oxazolone, showed a marked increase in cell content, presumably due to lymphocyte immigration. A surprisingly large proportion of these cells exhibit properties of B lymphocytes: the presence of surface Ig, lack of Thy-1-like antigen and responsiveness to lopopolysaccharide (LPS). The relationship between the presence of surface markerand responses to class-specific mitogens, of cells from the stimulated nodes, was established by testing fractionated lymphocyte populations. Enriched T cells did not react to LPS, whereas removal of cells with Thy-1 antigen by specific antisera eliminated the reactions to T mitogens but had little or no effect on the LPS response. The data thus suggest that B cells, which make up a small portion of the circulating lymphocyte pool, are selectively accumulated in lymph nodes stimulated by different immunogens, including T-specific stimulants. This interpretation contradicts the generally accepted assumption, that stimulat lymph nodes trap mostly T lymphocytes.

Evidence of 'K'-cell killing by alloactivated, Fc-receptor-bearing cytotoxic T lymphocytes

Upon in vivo alloactivation of Ig-anti-Ig column-purified splenic 'T' cells in lethally irradiated allogeneic recipients, a variable proportion of donor-derived cytotoxic T lymphocytes (CTLs) are able to bind IgG antibody-coated erythrocytes through surface Fc receptors (FcR) and form rosettes. The use of fractionation procedures based on the ability of these cells to form rosettes has enabled us to separate FcR-positive CTLs from FcR-negative CTLs and to examine the ability of these two cell populations to perform as effector cells in direct T-cell-mediated killing and in antibody-dependent cellular cytotoxicity. A series of experiments, either by direct isolation of the two cell populations or by deletion of the FcR-positive population by filtration through complexed immunoglobulin columns (Ig-anti-Ig), has shown both populations to be efficient in direct T-cell mediated cytotoxicity against the relevant target cell. The striking difference between the two populations is the exclusive ability of the FcR-positive population to function as effector cells in antibody-dependent cellular cytotoxicity (ADCC). Purification steps before in vivo alloactivation of our responding cells for the removal of 'B' cells and FcR-bearing cells with 'K'-cell activity, followed by procedures to remove phagocytic and adherent cells in the resulting immune spleen cell preparation and, finally, b y velocity sedimentation of the rosetting and nonrosetting blasts from the small lymphocyte population, has resulted in a population of FcR-positive cells 98% positive for the Thy 1.2 alloantigen. These fractionation steps and immunofluorescence criteria of purity strongly favor the contention that the ADCC activity within the FcR-positive T-cell population is indeed a property of the CTL itself.

Separation and properties of EA-rosette-forming lymphocytes in humans

Human peripheral blood lymphocytes were separated into subpopulations enriched or depleted with respect to B lymphocytes (Ig-bearing cells), T lymphocytes, (cell forming rosettes with sheep erythrocytes: E-RFC) and Fc receptor-bearing lymphocytes (EA-RFC). From the distributions and recoveries of the various cell types it could be concluded that there was very little overlap between Ig-bearing lymphocytes and EA-RFC. The latter cells partly belonged to "null" (non-T, non-B) cells; it was however demonstrated that 30 % of the EA-RFC were T cells (E-RFC). The lytic capacity in antibody-dependent lymphocytotoxicity (ADL) was shown to correspond with the proportions of EA-RFC in the various fractions. Non-T cells showed enhanced ADL activity when compared to the unseparated cells. Purified T cells populations also displayed ADL activity. Since the latter could not be due to contaminating non-T cells, this activity was ascribed to Fc receptor-bearing T lymphocytes.

Lymphocyte surface immunoglobulins: detection, characterization, and occurrence in disease of the lymphoid system

Surface immunoglobulins (Igs) of lymphocytes are of considerable interest because these molecules probably function as receptors for antigen, and knowledge of their molecular properties should provide information on the mechanisms of immune differentiation. The density and types of surface Ig on a cell provide markers useful in indicating the class of a lymphocyte and its stage of maturity. Moreover, knowledge of the specificities of the surface Ig of neoplastic lymphocytes might suggest the nature of agents involved in the generation of the disease. Two broad classes of lymphocytes, bone marrow-derived lymphocytes (B cells) active in antibody secretion, and thymus-derived lymphocytes (T cells) which mediate cellular immune reactions, and their subpopulations must be considered with reference to the nature, origin, and function of their surface immunoglobulin. This article analyzes direct and indirect methods for the demonstration of surface Igs and describes certain physicochemical properties of isolated surface Ig molecules. Roles of these surface molecules in recognition of antigen, initiation of all differentiation, and cooperation among lymphocytes and accessory cells are discussed.