T lymphocyte stimulation by hapten-conjugated macrophages: a model system for the study of immunocompetent cell interactions

Trinitrophenol reactive T-cell hybridomas recognize antigens that require antigen processing

Protein antigens must be taken up, processed, and displayed on the surface of antigen-presenting cells in association with major histocompatibility complex molecules before they can be recognized by T cells. Whether recognition of the haptens used to study allergic contact hypersensitivity in murine models similarly requires processing has not been determined. We analyzed whether presentation of trinitrophenol to trinitrophenol reactive T-cell hybridomas requires antigen processing by studying the effects of inhibitors of antigen processing and presentation on the ability of a syngeneic B-cell tumor (A20) to present trinitrophenol to a series of interleukin-2 producing, trinitrophenol specific, major histocompatibility complex class II-restricted T-cell hybridomas. The ability of trinitrophenol modified A20 cells to stimulate the hybridomas was completely inhibited by monoclonal, anti-trinitrophenol, or anti-Ia antibodies and was significantly reduced by paraformaldehyde fixation immediately after trinitrophenol modification. Trinitrophenol-modified A20 cultured at 37 degrees C for 2 h prior to fixation was significantly more effective at stimulating the hybridomas than trinitrophenol-modified A20 fixed immediately. The ability of A20 to present trinitrophenol was inhibited by chloroquine. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of trinitrophenol modified lymph node dendritic cells to stimulate the trinitrophenol specific hybridomas. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of A20 cells to present ovalbumin to ovalbumin-specific hybridomas as they had on the ability of trinitrophenol modified A20 cells to present trinitrophenol to the trinitrophenol specific hybridomas. One of seven T-cell hybridomas responded to trinitrophenol modified ovalbumin but not other trinitrophenol modified proteins. These results suggest that, at least in part, T cells in the contact hypersensitivity response to trinitrophenol recognize antigens that require processing and that trinitrophenol modified proteins can be recognized.

Activation and expansion of hapten- and protein-specific T helper cells from nonsensitized mice

Hapten- and protein-antigen-specific T helper cells are usually expanded in vitro from lymphocytes obtained from sensitized animals. In this paper we report on the primary activation and proliferation in vitro of T helper cells from nonsensitized animals by using syngeneic cultured epidermal Langerhans cells as a source of potent antigen-presenting cells. The primary in vitro proliferation was blocked with monoclonal antibodies to Ia molecules, to lymphocyte function-associated antigen 1 (LFA-1), and to L3T4. T helper cell populations sensitized in vitro to haptens and protein antigens showed hapten- and antigen-specific proliferation when restimulated in vitro with spleen cells. Besides its experimental usefulness, in vitro generation of syngeneic specific T helper cells may afford possibilities for adoptive immunotherapy.

Delayed-type skin reaction to 2,4-dinitrophenylated epidermal cells in guinea pigs with contact sensitivity to 2,4-dinitrochlorobenzene

Contact sensitivity (CS) induced by hapten has been thought to be analogous to delayed-type hypersensitivity, such as the Mantoux reaction, because of outstanding similarities between the two phenomena. It can be suggested that animals with CS respond also to intradermal injection of the conjugate of hapten and protein as well as to epicutaneous application of hapten. However, evidence against this has been reported. In the present experiments, delayed-type skin reaction (DSR) was successfully obtained in JY1 strain guinea pigs sensitized by painting the skin with 2,4-dinitrochlorobenzene using in vitro dinitrophenylated epidermal cell suspension (DNP-EC) as antigen for a delayed intradermal test. The experiment using anti-Ia alloantiserum and complement showed that the elicitation of DSR is due to the presence of Ia-positive cells (presumably Langerhans cells) among DNP-ECs. The delayed intradermal test with the conjugates such as haptenated ECs in the animals with CS is considered to be an experimentally useful way of analysing the antigen in the sensitivity.

A naturally occurring bone marrow-chimeric primate. II. Environment dictates restriction on cytolytic T lymphocyte-target cell interactions

Restriction on cytolytic T lymphocyte (CTL)-target cell-interactions are studied in the primate S. oedipus, a naturally occurring A + B----A bone marrow-chimeric species. We show that the T cell, B cell, and myelomonocytic progenitor cell populations are chimeric in this species. We selected animals for study that are populated by fully major histocompatibility complex (MHC)-disparate hematopoietic cell populations, using a functional assay system. We then developed an in vitro system for analyzing at the clonal level the genetic restrictions on the trinitrophenyl-specific CTL-target cell interactions of this species. In this system, we have shown that tolerance to foreign MHC determinants was not, of itself, sufficient to facilitate the generation of CTL specific for target cells expressing those foreign MHC determinants. Rather, a marked preference for the expansion of CTL clones with a restriction for target cells bearing the host animals' MHC determinants was seen. Hematopoietically derived cells did not affect the repertoire of these T lymphocytes. These studies represent the first demonstration of the phenomenon of an environment dictating interactional restrictions on CTL in a naturally occurring bone marrow-chimeric animal. This is also the first demonstration of the profound influence of the environment on the repertoire of the T lymphocyte in a primate species.

Selection of the delayed hypersensitivity T effector and T suppressor cell response by antigen-presenting macrophages

The T effector lymphocytes of delayed type hypersensitivity reactions (TDH) are regulated by a complex T suppressor (Ts) cell circuit. Induction of TDH cells requires Ia+ adherent cells as antigen-presenting cells. Little is known about the antigen presentation of the induction of Ts cells. We describe an experimental model in which TDH and Ts cells are induced separately by different antigen-presenting macrophages grown from bone marrow stem cells. Bone marrow derived macrophages grown in L cell-conditioned medium for various periods and labeled with 2,4-dinitrobenzene sulfonic acid differ in their ability to induce TDH and Ts cells in vitro. The functional activity of the two T subpopulations was assessed in vivo by epicutaneous challenge or sensitization with 2,4-dinitrofluorobenzene of mice receiving the in vitro educated cells. Ear swelling or suppression of swelling was recorded. It could be shown that 5-7 day bone marrow-derived DNP-labeled macrophages preferentially induced Thy 1+ Lyt 1+ antigen-specific TDH cells; 7-10 day old antigen-presenting bone marrow-derived macrophages induced preferentially Thy 1+ Lyt 2+ antigen specific Ts cells. Characterization of various phenotypic markers revealed different surface antigen expression and functional differences such as MIF responsiveness or transglutaminase activity on the two macrophage populations. These data support the concept that activation of the Ts regulatory circuit may require antigen presentation by specialized antigen presenting cells, characterized by certain surface and functional markers and different from those inducing preferentially TDH cells.

Selective induction of delayed hypersensitivity T-effector and T-suppressor lymphocytes in vitro by haptenized bone marrow-derived macrophages

The role of various subpopulations of antigen-presenting macrophages in the induction of T-lymphocyte subpopulations has been difficult to study in the past. We have used an in vitro system of bone marrow cell culture both to induce T-effector (TDH) and T-suppressor (Ts) cells active in delayed-type hypersensitivity. Bone marrow-derived macrophages (BM-MA) grown in Teflon bag cultures were allowed to attach to culture dishes and were pulse-labeled with 2,4-dinitrobenzene sulfonate (DNBSO3). Spleen cell lymphocytes from nonsensitized BALB/c mice were cocultured with antigen-pulsed or control BM-MA for 3 days. The lymphocytes were harvested, and injected iv into BALB/c mice which were challenged within 1 hr after injection by painting the right ear with 2,4-dinitrofluorobenzene (DNFB, effector test) or sensitized with DNFB on 2 days following iv injection of the cells and challenged 5 days later (suppressor test). Ear swelling was measured 24 hr later to assess the effector or suppressor function of the in vitro educated lymphocytes. BM-MA grown for 5 days (BM-MA 5) in L-cell conditioned medium induced only TDH cells (Thy 1+, Lyt 1+2-) whereas BM-MA grown for 10 days in conditioned medium induced only Ts cells (Thy 1+, Lyt 1-2+). In both cases, induced TDH and Ts cells were antigen specific. Functionally, induced Ts cells suppressed the afferent limb of the delayed response. When DNP-BM-MA 5 and DNP-BM-MA 10 were used to induce TDH or Ts cells in vivo by subcutaneous or intravenous injection respectively, only BM-MA 5 were able to sensitize recipient mice. Both 5- and 10-day macrophage populations induced Ts cells in vivo. Functionally, these Ts cells appeared to act on the efferent limb of the delayed reaction. We conclude that different populations of antigen-presenting macrophages can preferentially induce TDH or Ts cells, perhaps depending on antigen presentation in association with class II antigens or on the functional state of the antigen-presenting cell.

Induction of hapten-specific lymphoid cell proliferation by liposome-carrying molecules from haptenated epidermal cells in contact sensitivity

Liposomes containing the extract of trinitrophenylated (TNP) epidermal cells stimulated lymph node cells from TNCB-sensitized mice effectively. Optimal stimulation was achieved by the liposome containing 0.06 microgram of the extract of TNP epidermal cells/microgram of phospholipid at a concentration of 20 micrograms phospholipid/ml. The response was hapten-specific and macrophage-dependent. UV irradiation of the epidermal cells abolished their ability to stimulate the lymph node cells. Furthermore, the liposomes containing the extract of TNP epidermal cells treated with anti-Ia and complement failed to stimulate the lymph node cells. The liposomes recovered their reactivity when nonhaptenated Ia antigen-rich epidermal extract was added. Taken together, it is likely that haptenated molecules and Ia antigen on the liposome stimulated T-lymphocytes in the presence of macrophages.

Molecular signals in antigen presentation. I. Effects of interleukin 1 and 2 on radiation-treated antigen-presenting cells in vivo and in vitro

In order to clarify the nature of the defect in the process of antigen presentation caused by uv radiation, low-density spleen cells were used as a potent APC source in a hapten-specific cytolytic T-cell (Tc) system. It was demonstrated that IA+ weakly adherent low-density spleen cells, when directly coupled with azobenzene arsonate (ABA), led to the activation ABA-specific Tc. When these APC were exposed to uv radiation (12 J/m2/sec) for 30 sec, their ability to lead to Tc activation was markedly inhibited. The defect imposed by uv radiation could be specifically bypassed by the addition of small amounts of homogeneous IL-1 or IL-2. This led to the specific activation of ABA-reactive H-2-restricted Tc. The purified IL-1 was also found to bypass the systemic defect imposed in vivo by external uv radiation of mice. This may indicate a potential therapeutic role for IL-1.

Human class II major histocompatibility antigen beta-chains are derived from at least three loci

Class II antigens of the major histocompatibility complex (MHC) consist of two glycosylated, membrane-integrated polypeptide chains. These cell surface-expressed molecules are involved in several immunobiological events involving cell-cell interactions, most of which seem to require that genetically identical class II antigens, or other molecules controlled by the same region of the MHC, are expressed on the interacting cells. The extensive genetic polymorphism of the class II antigens has rendered analyses in the human system of the number of non-allelic species of class II antigens difficult, although several laboratories have reported the existence of at least two types of human class II antigens. Here we present the results of experiments using restriction enzyme digestions and separation of DNA from individuals homozygous for the MHC followed by hybridization to human class II antigen alpha- and beta-chain cDNA probes. While the alpha-chain probe gave only a single hybridization band, the various beta-chain probes revealed a more complex pattern that is consistent with the existence of at least three separate beta-chain genes or pseudogenes in the human MHC.

Nature of the antigenic complex recognized by T lymphocytes. VIII. Specific inhibition of the stimulatory capacity of antigen-pulsed hapten-modified peritoneal exudate cells by anti-hapten antibody

When macrophages which were pulsed with soluble protein antigens and then modified with 2,4,6-trinitrobenzenesulfonic acid (TNBS) were cultured with primed T cells in the presence of anti-2,4,6-trinitrophenyl (TNP) antiserum, a marked inhibition of the T cell proliferative response specific for the soluble protein antigen under study was observed. Inhibition of the proliferative response required that the protein antigen under study be easily susceptible to conjugation with TNBS. A lag period of 1-3 h must elapse following pulse exposure to the protein antigen and prior to TNP modification for anti-TNP antibody to exert an inhibitory effect, which suggests that processing of antigen in an intracellular site might occur with subsequent reexpression of antigen on the macrophage surface. It was hypothesized that anti-TNP antibody inhibits T cell proliferation by capping and shedding of TNP-modified determinants of the nominal antigen as well as TNP-modified cell surface proteins from the macrophage membrane. The failure of others to demonstrate an effect of anti-antigen antibody on T cell activation can best be explained as secondary to the low density of antigenic determinants on the macrophage membrane with resultant low-affinity binding of antibody to antigen.

Complete amino acid sequence of an HLA-DR antigen-like beta chain as predicted from the nucleotide sequence: similarities with immunoglobulins and HLA-A, -B, and -C antigens

The complete nucleotide sequence of an HLA-DR antigen-like beta-chain cDNA clone was determined. The 1,080 base pairs include the complete coding region and most of the untranslated portion. The predicted amino acid sequence has 229 residues. The beta chain contains two immunoglobulin-like disulfide loops and a 21-amino acid residue membrane-integrated segment. Ten amino acid residues reside on the cytoplasmic side of the plasma membrane. The single asparagine-linked carbohydrate moiety is attached to asparagine-19. The NH2-terminal 91 residues of the beta chain are homologous to the corresponding region of HLA-A, -B, and -C antigen heavy chains. Residues 92-192 of the beta chain display statistically significant homology to members of the immunoglobulin family, beta 2-microglobulin, and the immunoglobulin-like domain of HLA-A, -B, and -C antigen heavy chains. These data establish that the major histocompatibility antigens of class I and class II type and the constant regions of immunoglobulins are evolutionarily related.

Human T cell lines with antigen specificity and helper activity

Human T blasts, obtained by stimulation of peripheral blood mononuclear cells (PBM) with tetanus toxoid, diphtheria toxoid or Candida albicans, were expanded in long-term culture using alternate periods of antigen restimulation and growth in media containing interleukin 2. The cells gave a proliferative response only to the antigen originally used for stimulation. Such as response was strictly dependent upon the presence of autologous but not of allogeneic mitomycin C-treated mononuclear cells. When added to autologous PBM depleted of E-rosetting cells together with the specific antigen, the T blasts induced a polyclonal proliferation and differentiation of B cells. Allogeneic B cells were activated by antigen-stimulated T blasts only in the presence of irradiated mononuclear cells autologous to the responding T blasts. The above responses seemed not to be regulated solely by the release of soluble factors; apparently cell to cell interactions had to take place to obtain an efficient B cell activation.

Specificity of antigen binding by T cells; competition between soluble and Ia-associated antigen

Competitive antigen binding experiments were performed with purified T and B cells of C3H.SW (H-2b) mice. As antigen, (T,G)-A--L [poly-L(Tyr,Glu)-poly-DL-ALa-poly-L Lys] was used, both in an Ia-containing form, released by adherent cells (IAC-Puri and Lonai, Eur. J. Immunol. 1980. 10:273), and in regular solution. It was found that regular (T,G)-A-L did not compete with the binding of 125I-labeled-IAC-(T,G)-A--L even at a 10(4)-fold excess, whereas IAC-(T,G)-A--L inhibited binding at 10-fold excess. The specificity of (T,G)-A--L binding to high-responder T and B cells was compared by using related branched synthetic copolymers as competitors. B cells cross-reacted with (T,G)-A--L, (H,G)-A--L, (G)-A--L and (T,G)-Pro--L. In contrast, antigen binding C3H.SW T cells cross-reacted only with (T,G)-A--L and (Phe, G)-A--L to both of which they are Ir gene-controlled high responders. Evidence for the Ir gene control of IAC-binding T cells was obtained by showing that high X low responder F1 hybrid T cells preferentally bind IAC-(T,G)-A--L processed by processor cells deriving from the high-responder parental strain. These data are interpreted to suggest that T cells have high affinity for antigen plus self Ia complexes, whereas they have a much lower, if any, affinity for free antigen. It also follows from the results that the structure of the complex ligand may have a role in defining the specificity, H-2 restriction and Ir gene control of T cells.

Modulation of suppressor mechanisms in allergic contact dermatitis: 2. Inhibition of suppressor T-lymphocytes by Corynebacterium parvum

Pretreatment of BALB/c mice with Corynebacterium parvum inhibited the induction of tolerance to the contact sensitizing agent 2,4-dinitrofluorobenzene induced by intravenous injection of DNBSO3. The suppressive effect on tolerance induction has further been analyzed by adoptive transfer experiments. Injection of C. parvum intraperitoneally (0.7-2.8 mg/mouse) before injection of the tolergen inhibited the generation of T-suppressor cells as shown by transfer of spleen cells from the tolerized donor to naive recipients. Pretreatment of the recipients of the suppressor T-cells from tolerized animals with C. parvum also inhibited the function of these cells in the recipient animals. Time-kinetic experiments suggested that more than one mechanism appeared to be responsible for the tolerance induced by DNBSO3; C. parvum (probably via activated macrophages) suppressed tolerance which is mediated by T-suppressor lymphocytes. These results suggest that T-suppressor lymphocytes may--similarly as T-helper cells--be modulated by an activated monocytic-phagocytic system.

The peritoneal antigen-presenting macrophage: control and immunogenic properties of distinct subpopulations

The control of the immunogenic antigen-presenting capacity of different subpopulations of thioglycollate-induced peritoneal macrophages had been investigated. The experiments revealed the existence of two major subpopulations of macrophages, only one of which was highly efficient in educating antigen-specific T cells. The other subpopulation, while highly phagocytic, was devoid of antigen-presenting capacity. Further analysis, using specific antisera directed at H-2I region gene products, revealed that the immunogenic antigen-presenting population expressed H-2I region-controlled membrane antigens. Searching for cellular elements which control the differentiation of this antigen-presenting macrophage subpopulation, it was found that its function was strictly controlled by T cells. T cell-deficient mice (nu/nu) failed to generate a functional antigen-presenting macrophage subpopulation. Transplantation of mature T lymphocytes to T cell-deprived mice restored the immunogenic function of their antigen-presenting macrophage subpopulation. Transplantation of mature T lymphocytes to T cell-deprived mice restored the immunogenic function of their antigen-presenting macrophages. The results obtained suggest the existence of heterogeneity of functions among macrophage subpopulations and add a new regulatory function for T cells.

Modulation of suppressor mechanisms in allergic contact dermatitis: 1. Effect of C. parvum on the induction phase of contact allergy

The effect of a pretreatment with corynebacterium parvum (C. parvum) on contact allergy in BALB/c mice was studied. Mice sensitized with 50 microliter (supraoptimal dose) 2.4-dinitrofluorobenzene (DNFB, 0.5%) showed a suppressed response as measured by ear swelling after painting the right ear with 0.3% DNFB in comparison to an allergic response obtained with an optimal sensitization dose (15 microliter DNFB 0.5%). By transfer of spleen cells from donors sensitized with a supraoptimal or an optimal dose to recipients either challenged ro sensitized shortly afterwards with DNFB it could be shown that less functionally active immune T-lymphocytes of the delayed hypersensitivity type and significantly more suppressor T-cells were induced in supraoptimally sensitized mice in comparison to the optimally sensitized animals. Intraperitoneal injection of C. parvum (2.8 mg/mouse) one week before sensitization enhanced the contact allergic response in mice sensitized with a supraoptimal dose of DNFB, with little effect on the response in optimally sensitized animals. Further analysis of this enhancement in transfer experiments showed that C, parvum selectively suppressed the generation and/or functional expression of T-suppressor cells and, probably by this mechanism, increased the number of functionally active T-immune lymphocytes. It is proposed that possibly by activation of the immune system C. parvum will suppress suppressor cells in contact allergy and by this mechanism might facilitate sensitization to the contact allergen.

Antigen-presenting cell function in induction of helper T cells for cytotoxic T-lymphocyte responses: evidence for antigen processing

We demonstrate that splenic adherent cells (SACs) play an active role in the presentation of H-2Kk antigen for an alloreactive cytotoxic T-lymphocyte (CTL) response. If antigen is incubated with SACs for 12 hr, they will provide maximal stimulation and present the antigen in the context of their Ia molecules. UV irradiation of these SACs, prior to the 12-hr incubation with H-2Kk antigen, abrogates this stimulatory capacity. Macrophage-bound antigen is not sufficient for stimulation of a response; a second signal is required as well, that, in our system, is provided by phorbol myristic acetate. The SACs are involved in the activation of helper T cells; however, they are not required for presentation of antigen to the precytotoxic T-lymphocyte, which requires two signals for activation, one provided by antigen and the other by a T-cell-derived helper factor.

Recognition of heterologous cells by macrophages. I. Species recognition by mouse and guinea pig macrophages in the phagocytosis of heterologous thymocytes

The ability of macrophages to recognize homologous and various heterologous cells was studied in mice, rats, and guinea pigs, in terms of the in vitro phagocytosis of non-opsonized viable thymocytes by macrophages. Mouse, rat, and guinea pig macrophages were found to phagocytize actively thymocytes from certain heterologous animals, including chickens. For instance, mouse macrophages displayed conspicuous phagocytic activities against chicken and duck thymocytes, moderate activities against guinea pig and frog thymocytes and weak activities against rat and mouse thymocytes. On the other hand, guinea pig macrophages revealed a different behaviour: they ingested only chicken thymocytes. These observations strongly suggested that mammalian macrophages possess some ability to discriminate homologous from certain heterologous thymocytes. The results, however, did not necessarily support the idea that the degree of phagocytosis is simply related to the phylogenetic distance between the animal species from which thymocytes and macrophages originated, because of the apparent exception in the mode of phagocytosis by guinea pig macrophages. Evidence demonstrating that antibodies are not involved in this phenomenon will be presented in the accompanying paper.

Cellular interactions in the generation of cytolytic T lymphocyte responses: role of Ia-positive splenic adherent cells in presentation in H-2 antigen

Splenic adherent cells are required for generation of both primary and, at limiting antigen dose, secondary allogeneic responses of cytolytic T lymphocytes to intact stimulator cells. Secondary responses to purified allogeneic plasma membranes or purified H-2Kk antigens in liposomes are also dependent upon splenic adherent cells. Generation of these responses requires the presence of an Ia-positive. Thy 1,2-negative, radiation-resistant cell in the splenic adherent cell population that is adherent to glass, plastic, and nylon wool. Stimulation of cytolytic T lymphocyte precursors with purified H-2Kk alloantigen bound to Ia+ splenic adherent cells is 10-20 times more efficient than stimulation with antigen added directly to culture. Furthermore, a marked decrease in the response of cytolytic T lymphocytes to liposomes was observed when antiserum against Iad specific for the Ia of the responder cells was added to culture. These results demonstrate that, for purified proteins of the major histocompatibility complex, antigen presentation by Ia+ splenic adherent cells plays a role in the generation of a cytolytic T lymphocyte response.

The role of the major histocompatibility complex in the regulation of macrophage-T lymphocyte interaction

The proliferative response of guinea pig T lymphocytes which have been primed in vivo can only be induced by antigen-pulsed syngeneic macrophages. The development of techniques to prime T lymphocytes in vitro has allowed us to demonstrate that the genetic restriction on the interaction of the macrophage and T lymphocyte is regulated by the Ia antigens of the macrophage used during the initial sensitization step. Following removal of alloreactive cells, T cells can be sensitized to antigen-treated allogeneic macrophages. It thus appears likely that T cells do not recognize antigen per se, but can only be sensitized to antigen-modified membrane components or to complexes of antigen combined with certain membrane molecules. We postulate that the Ia antigens themselves are the products of the immune response genes and function in both macrophages and B lymphocytes as antigen recognition structures.

Role of I-region gene products in macrophage induction of an antibody response. II. Restriction at the level of T cell in recognition of I-J-subregion macrophage determinants

The effect of specific anti-I-J reagents on macrophage-T cell interactions was studied in an in vitro antibody response to burro erythrocytes. Macrophages were prepared from the spleens of F1 hybrid mice whose parental strains differed at the I-J subregion. Two F1 hybrids were used for these experiments, [B10.A(3R) X B10.A(5R)]F1 and [B10.S(9R) X B10.HTT]F1. F1 macrophages responded equally well with F1 T-B cells or with T-B cells of either parental strain. When F1 macrophages were pretreated with anti-I-J serum (without complement) specific for one parental haplotype, they were only able to cooperate with T helper (TH) cells of the unblocked haplotype and with F1 TH cells. Identical results were obtained with (Jb X Jk)F1 and (Js X Jk)F1 mice. The results indicate that TH cells possess genetically restricted receptors for macrophage I-J-subregion gene products and that the interaction between this receptor and the macrophage I-J-subregion determinants is essential for the initiation of a primary in vitro antibody response to an erythrocyte antigen.

HLA-D-restricted antigen activation of sensitized T lymphocytes: studies on the ability of HLA-D/DR-expressing B lymphocytes to substitute for macrophages in antigen activation

The proliferative response of sensitized human T lymphocytes to purified protein derivative (PPD) and to trinitrophenyl (TNP)-conjugated autologous cells in vitro is restricted by self HLA-D/DR determinants. Here we report that the PPD-specific response is strictly related to the content of phagocytosing cells (macrophages, Mphi) in the cultures and that an optimal PPD response occurred at a T/Mphi ratio between 10:1 and 5:1. B-cell-enriched suspensions, which also express the HLA-D/DR determinants, were not able to replace the macrophages in this HLA-D/DR-restricted response. On the other hand, TNP-treated similarly prepared B cells were in most instances effective in inducing a secondary TNP-specific response of in vitro-sensitized T cells.

Specific binding of T lymphocytes to macrophages IV. Dependence on cations, temperature and cytochalasin B-sensitive mechanisms

Peritoneal exudate lymphocytes (PEL) from immune guinea pigs adhere to macrophages carrying the relevant antigen and are thereby stimulated to proliferate in culture. The resultant PEL represent a population highly enriched with regard to their capacity to specifically rebind to antigen-pulsed macrophages. We have studied the mechanisms underlying specific binding of lymphocytes to macrophages by examining the effects of physical and chemical modifications of the two cell types. Specific binding was inhibited by fixation of cells, metabolic inhibitors, low temperatures, cytochalasin B and divalent cation depletion. After specific binding has taken place, cation depletion, but not cytochalasin B or low temperatures, disrupts binding. These observations indicate that specific binding occurs by a series of discrete events that can be operationally distinguished.

In vitro sensitization of human T lymphocytes to hapten (TNP)-conjugated and non-treated autologous cells is restricted by self-HLA-D

By co-culturing human T lymphocytes with TNP-treated autologous B lymphocytes and macrophages for 10 days in vitro, sensitization to TNP-treated autologous cells could be detected in a proliferative assay. By restimulation with different types of allogeneic cells and with cells from donors compatible or incompatible for the HLA-ABC or -D determinants, results were obtained suggesting that the TNP-specific response was restricted by the HLA-D but not the -ABC antigens of the autologous priming cells. Furthermore, our experiments demonstrate that T lymphocytes can also be primed against non-treated autologous cells in vitro and suggest that the HLA-D determinants may be involved also in this auto-sensitization.

Influence of thymus genotype on acquisition of responsiveness in delayed-type hypersensitivity

Antigen-pulsed macrophages (Mph) could sensitize syngeneic mice for delayed-type hypersensitivity (DTH) and also elicit sensitivity from mice sensitized to antigen in adjuvant provided these were syngeneic or semi-allogeneic to the strain providing the Mph. Sensitivity could not be elicited with antigen-pulsed allogeneic Mph. Antigen-pulsed Mph from low-responder (LR) strains could not sensitize LR mice nor F1 hybrids between responder (R) and LR strains. Normal F1 mice could be sensitized to respond to antigen presented on Mph or either parental type (i.e. P1 or P2): if, however, they were sensitized to antigen on P1 Mph, DTH transfer was restricted to naive P1 mice, not to P2 (restriction imposed by priming). F1 T cells derived from stem cells differentiating in a P1 thymus graft could be sensitized but could transfer sensitivity only to naive P1 mice, not to P2 (restriction imposed in thymus). When an antigen under Ir gene control was used, LR derived T cells differentiating in an (R X LR)F1 thymus could be sensitized but only if antigen was presented on (R X LR)F1 Mph not on LR Mph. Totally allogeneic chimaeras could be sensitized but only if given antigen in association with the appropriate Mph. These findings suggest that restriction of T cell activities can be imposed as a result of priming in some cases and as a result of differentiation within the thymus in others. LR strains appear to have a lesion at the level of antigen presentation by Mph; whether they also have a defect at the level of generation of T cell repertoire cannot be determined from the present investigations.