Rejected human renal allografts: recovery and characteristics of infiltrating cells and antibody

Viable infiltrating host leukocytes have been isolated from 10 rejected human renal allografts, removed 1 to 67 months after transplantation. The cell populations have been identified by surface characteristics and their cytotoxic capacities were assessed. A heterogenous population of cells of host origin accumulated in the grafts, including T and B lymphocytes, Fc+ cells, and macrophages. Using a 51Cr release assay, specific cytotoxicity against donor alloantigens was determined. Cytotoxicity of the infiltrating cells was almost invariably greater than cytotoxicity mounted by recipient peripheral blood lymphocytes. Deletion studies confirmed previous work and suggested that T cells were primarily responsible for cytolysis in early acute rejection; non-T cells more often in late chronic rejection. Antibodies eluted from the grafts demonstrated both specific antidonor and nonspecific activity as well as cross-reacting anti-HLA activity. Allograft morphology was examined and cellular and humoral host responses were assessed. These studies emphasize the complexities of immune responses produced by the host against transplanted tissues.

Stimulation of lymphocyte proliferation by non-lymphoid porcine tissue cells

Cultured porcine non-lymphoid cells, characterized by biochemical and morphological criteria, were derived from different tissues of individuals typed by serological and mixed lymphocyte culture methods for gene products of the major histocompatibility complex. These cultured cells have been used as stimulators in mixed lymphocyte-tissue cell cultures in order to investigate (1) the magnitude, kinetics and dose-dependence of lymphocyte transformation caused by tissue cells compared with that caused by lymphocytes as stimulators; (2) the relationship between the expression of serologically detected Ia-like antigens by tissue cells and their ability to cause lymphocyte transformation; (3) the genetic control of stimulation by tissue cells and by lymphocytes and (4) the expression and genetic control of lymphocyte stimulatory properties restricted to tissue cells and absent from lymphocytes. It has been shown that some but not all kinds of tissue cells can stimulate allogeneic lymphocytes strongly and that the characteristics of such stimulation are similar to those observed in mixed lymphocyte cultures. Strong stimulation by tissue cells does not always correlate with the expression of serologically detectable Ia-like antigens, but appears to be controlled by the major histocompatibility complex. There is evidence that certain tissue cells possess lymphocyte stimulatory properties not shared by lymphocytes. Preliminary data suggest that such tissue cell specific stimulation is not controlled by the major histocompatibility complex, though more detailed genetic analysis is required.

Mechanisms involved in the weak alloimmunogenicity of Thy-1 on mouse brain

Immunization of mice with allogeneic brain homogenates fails to elicit an appreciable response to the Thy-1 antigen. The aim of the present study was to determine the mechanism of the low immunogenicity of allogeneic brain. Immunization of C3H mice with freshly prepared mixtures of AKR/J thymus cells with either AKR/J or C3H brain homogenates elicited a primary response to the Thy-1.1 antigen as effectively as immunization with AKR/J thymus cells. When the mixtures were incubated overnight prior to injection, only AKR/J brain homogenate but not C3H brain homogenate abrogated the capacity of AKR/J thymus cells to elicit an anti-Thy-1.1 response. Suppressor T cells did not seem to be responsible for the inability of brain to elicit an anti-Thy-1 response, as mice that received cyclophosphamide 2 days prior to injection of brain did not produce Thy-1 antibodies. Antigenic competition also did not seem to be the cause for the weak immunogenicity of Thy-1 on brain, as mixtures of thymus and brain were capable of eliciting a primary response. When spleen cells from mice hyperimmunized against Thy-1 were transferred to normal syngeneic mice, subsequent immunization with brain homogenate was capable of eliciting Thy-1 antibodies. These results indicate that Thy-1 on brain may resemble a hapten, in being incapable of eliciting a primary immune response, but behaves like a complete antigen in boosting a secondary response.

Cytotoxic and proliferative lymphocyte responses to allogeneic and xenogeneic antigens in vitro

In vitro lymphoproliferative responses to foreign histocompatibility antigens are phylogenetically restricted. Responses occur most readily to allogeneic or closely related xenogeneic leucocytes, but not to unrelated xenogeneic cells. Specific cytotoxic T cell responses to foreign histocompatibility antigens show the same phylogenetic restriction. This lack of xenoreactivity is not due to a lack of precursor cells for the xenoantigens; guinea-pig lymphocytes, although normally unresponsive to mouse antigens, have a similar precursor frequency for these antigens as do lymphocytes of allogeneic mouse strains. Specific cytotoxic responses of guinea-pig lymphocytes to mouse antigens can be generated if a factor released from con A stimulated guinea-pig spleen cells is added to the culture medium. The factor produced by con A-activated spleen cells (CS) is also phylogenetically restricted in its action; CS must be obtained from animals homologous with the donor of the responding lymphocytes.

Delayed-type hypersensitivity to allogeneic cells in mice. III. Sensitivity to cell-surface antigens coded by the major histocompatibility complex and by other genes

DTH could be induced to cell-surface antigens coded by either H-2 or non-H-2 genes. Sensitivity was more readily induced across I region than across K- or D-region differences. The presence of an I-region difference during sensitization did not significantly increase the DTH response to K- or D-region-coded antigens. Macrophage processing appeared to be the major route of sensitization to background antigens. Thus, high levels of sensitivity were achieved equally well using viable or disrupted cells, the response was independent of the H-2 haplotype of the allogeneic cells, and transfer was restricted to the K end of the host H-2 complex. Although sensitization to H-2 antigens was obtained with disrupted cells, transfer of sensitivity against viable cells was unrestricted. This suggests a minor role for macrophage processing in sensitization to H-2 antigens.

Alloantigen bound to agarose beads and syngeneic carrier cells are capable of stimulating mouse cytolytic T lymphocytes in vitro

Bead-bound antigen was prepared by coupling alloantigen covalently to agarose beads. Alloantigen-bearing syngeneic carrier cells were prepared by dilution of detergent solubilized alloantigen in the presence of syngeneic spleen cells. Both types of antigen were compared to spleen cells and reconstituted membrane fragments for the ability to stimulate cytolytic thymus-dependent lymphocytes in vitro. All these types of antigen could stimulate immune but not nonimmune spleen cells to form cytolytic T lymphocytes. The amount of lytic activity obtained with the bead-bound antigen was found to be only dependent upon the amount of H-2 antigen present in the culture and independent of the number of beads.

T cells recognize minor histocompatibility antigens on H-2 allogeneic cells

B10.A animals were rendered tolerant to B10.M spleen cells by injection of (B10.A X B10.M)F1 cells into neonates. Adult animals accepted B10.M skin grafts and failed to generate cytotoxic effector cells in vitro against B10.M H-2 antigens. In vivo inoculation of tolerant animals with A.CA spleen cells, followed by in vitro challenge with similar cells, resulted in the generation of cytotoxic effector cells that had specificity for the A strain minor histocompatibility (H)-antigens in the context of the H-2f haplotype. If these animals were boosted in vitro with A strain spleen cells, cross-priming could be demonstrated, whereby the cytotoxic effect was restricted by the H-2a haplotype. These data indicate that at least two sets of T cells co-exist in tolerant animals, one capable of recognizing antigens in the context of the host H-2 haplotype, and the other able to recognize antigens in the context of the tolerated H-2-allogeneic haplotype. Because tolerant animals inoculated with A-strain spleen cells in vivo and boosted in vitro with A.CA spleen cells failed to generate a cytotoxic effect against A.CA, it is unlikely that minor H-antigens need to be processed by host lymphoreticular cells.

Active immunization of female rabbits with purified rabbit acrosin and effect on fertility

Acrosin immunogen was purified from rabbit testes by sequential acid extraction, ammonium sulfate fractionation, cation-exchange, and affinity chromatography. Twelve females received intradermal injections of purified acrosin in Freund's complete adjuvant followed by a booster injection 6 weeks later. A radioimmunoassay for rabbit acrosin was developed and used to monitor the immune response of the recipients. The females were mated at the time when serum titers of acrosin antibodies were maximal. Four of the animals did not become pregnant, and three of these had the highest antibody titers in the total group. The remaining eight rabbits delivered normal litters at term. Of four control females (immunized with bovine serum albumin), one did not become pregnant. The pregnancy rates for the control and acrosin-immunized rabbits were 75% and 67%, respectively. It is concluded that, although active immunization with acrosin had no significant effect on fertility, the antibody titer produced may be a factor.

Frequency of allogeneic helper T cells responding to whole H-2 differences and to an H-2K difference alone

Limiting dilution analysis was used to determine the frequency of splenic T cells that are stimulated by alloantigen to give help in a primary antibody response to SRBC. Several haplotype combinations were tested. A semilogarithmic plot of the fraction of nonresponding culture as a function of the number of T cells added to excess B cells gave a straight line intercepting with the origin. Thus a single cell-type was limiting, which was required to help B cells respond to SRBC. The frequency of syngeneic precursors of T helper cells specific for SRBC ranged from 1/10,000 to 1/55,000 with a mean of about 1/20,000. Allohelpers generated by whole H-2 differences gave precursor frequencies that ranged from 1/1000 to 1/7000 with a mean of about 1/2500. Thus allohelpers to whole H-2 differences were approximately 8-fold more frequent than SRBC-specific helpers. When the stimulation was limited to the H-2K difference between the mutant B6.C-H-2ba and wild-type B6, frequencies of from 1/2600 to 1/7900 allohelpers were found with a mean of about 1/5000, approximately half the frequency of allohelpers to whole H-2 differences. Thus some, but probably not all, of the magnitude of allogeneic halp can be attributed to the high frequency of helper T cells that respond to a given alloantigen.

Generation of effector cells from T cell subsets. I. Similar requirements for Lyt T cell subpopulations in the generation of alloreactive and H-2 restricted killer cells

Lyt T cell subsets involved in the generation of H-2 restricted and alloreactive cytotoxic effector cells were analysed using anti Lyt antisera. Our data show that Lyt 1, 2, 3+ T cells are required for the induction of primary and secondary H-2 restricted and TNP-specific killer cells. In contrast, primary and secondary H-2 restricted and virus-specific T effector cells were obtained from selected Lyt 2, 3+ T cell populations and were not dependent on the presence of Lyt 1, 2, 3+ T cells. Allogeneic responses to selected K, I, or D region differences were obtained only in the presence of Lyt 1, 2, 3+ T cells; yet alloreactive killer cells were effectively generated from selected Lyt 2, 3+ T cell popluations deprived of Lyt 1, 2, 3+ T cells, when responder and stimulator cells differed at either K + D, K + I, I and D regionre is no qualitative difference between alloreactive and H-2 restricted cytotoxic responses in their requirements for particular Lyt T cell subsets. The findings indicate that the number of different antigenic determinants rather than their association with MHC self determinants is critical for the requirement of Lyt 1, 2, 3+ T cells during the sensitization phase.

Fetal bone grafts do not elicit allograft rejection because of protecting anti-Ia alloantibodies. Implications to the immune survival of fetuses in allogeneic mothers

In a previous study we showed that allografts of BN fetal bone, unlike allografts of adult bone, are not rejected by allogeneic recipients of the Lewis strain in spite of the existence of major histocompatibility complex (MHC) incompatibility between donors and hosts. In the present study, we analyzed the relationships existing between the host and fetal tissue that determine graft survival. We found that (1) the fetal BN graft, unlike adult grafts, induces in Lewis recipients a vigorous humoral response consisting mainly in the production of IgG antibody that seems to be directed against antigens of Ia-like specificities. (2) The BN rats are genetically defective in their capacity to respond to determinants and thus are not capable of producing anti-Ia antibodies; in accordance, Lewis fetal bone grafts are rejected by the BN recipients. (3) Chondrocytes isolated from fetal mouse bones do express Ia antigenic determinants. We suggest that the survival of an allogeneic fetal graft in an immunologically intact recipient depends on an active and selective immune response directed against the Ia components associated with the MHC on the embryonic and fetal cells. On the basis of these notions, we propose that the capacity of Ia determinants expressed on cells of the embryo, to elicit anti-Ia and IgG alloantibodies in the pregnant mother, determines the capacity of the embryo to escape rejection by the histoincompatible mother.

A syngeneic anti tumor serum recognizing a complex H-2 alloantigen

A methylcholanthrene induced tumor of BALBc (H-2d) origin had a high rate of spontaneous regression when transplanted into syngeneic animals. The tumor induced in BALB/c mice iso-antibodies with high anti-tumor cytotoxic activity. A specificity analysis of such BALB/c anti MCG4 sera revealed that the antibodies were directed against a tumor antigen which is very similar to H-2- alloantigens (e.g. H-2.5) expressed on normal cells of certain foreign mouse strains. The sera also reacted with nine out of ten B10.W congenic strains bearing H-2wi haplotypes derived from wild mice. Whether the tumor antigen is identical with foreign H-2 antigens or only cross-reactive cannot be decided at present.

Contrasting effects of H-2 and Mls immunization on the polyclonal mitogenicity of murine lymphocytes

During the immune response to H-2 and Mls alloantigens, murine lymphocytes showed altered sensitivity to polyclonal mitogens. The reactivity to the T-cell mitogen PHA followed a similar pattern in both H-2 and Mls-immunized mice while the reactivity to the B-cell mitogen LPS was contrasting in the two groups. In the former group, the response exceeded control levels by the seventh day after immunization and then gradually dropped below control levels; the response of Mls-immunized lymphocytes dropped below control levels soon after immunization and remained so for the period of study. Nylon wool column-purified Mls-immunized B cells also showed a suppressed reactivity to LPS, while the T-enriched populations from Mls-immune mice when added to normal B cells lowered their LPS reactivity. Soluble factors derived from clutures of Mls-immune lymphocytes had a suppressive effect on normal B cells.

Xenoserum-induced cytolytic "T" cells: polyclonal specificity with an apparent "anti-self" component, and cooperative induction

Mice were primed in vivo by injection of fetal calf serum (FCS) and their spleen cells were incubated in vitro for 5 days in medium containing 10% FCS. This resulted in the development of cytolytic activity, which was most probably due to "T" cells, since effector cells 1) were sensitive to anti-Thy 1 antiserum or monoclonal antibodies in the presence of complement, 2) were not retained on Ig-anti Ig columns, 3) did not develop from "nude" spleen cells. Further arguments for the T cell nature of these effector cells came from their specificity. Blocking experiments using unlabeled competitor cells demonstrated that FCS-induced cytolysis was polyclonal, with clones recognizing allogeneic or syngeneic determinants possibly related to allo or self H-2. In keeping with polyclonality, cytolysis tested on any given target cell was greatly increased by adding Concanavalin A during the cytolysis test. Experiments were made to investigate whether in particular the anti-self cytolytic activity was directed against FCS determinants. We feel that this possibility, although not formally excluded, was made unlikely. The polyclonal specificity at the effector stage stood in sharp contrast to the serum specificity at the induction stage (reported elsewhere). We demonstrated that these two sets of specificities corresponded to two sets of specific cells. A first population of FCS-primed cells had "promoter" activity, in the sense that it could trigger a second population of "precursor" cells to differentiate into polyclonally cytolytic T cells.

Hypothesis on the origin of the strong alloreactivity

The high proportion of alloreactive T lymphocytes and many of the available data on T cell receptors can be explained by one single hypothesis with four basic assumptions: A) The functional induction of T lineage cells in the thymus inherently causes a selection for V-regions that bind to major histocompatibility antigens (MHA). The type of MHA determines the functional pathway of the T cell. B) This process selects with the highest probability for binding sites with high affinity for the self-MHA, yet binding sites with high affinity for non-self-MHA and low affinity for self-MHA will also be selected with a low but finite probability. C) This positive selection for self-MHA binding V-regions is followed by a rigorous selection against self-reactive T cells during the subsequent thymic or post-thymic phase of tolerance induction. D) Most crucial for the hypothesis is, finally, the assumption that the second (negative) selection operates with a higher affinity threshold than the first (positive) selection. The negative selection thus spares T cell clones with low affinity for self-antigens. This provides a strong selective advantage for two major groups of cells, namely alloreactive cells most of which recognize nonself-MHA in complex with nonpolymorphic non-MHA determinants, and cells that recognize nonself-determinants in complex with self-MHA with different degrees of restriction. One of the predictions of this hypothesis is that the proportion of alloreactive cells is relatively small among the T lineage cells that leave the thymus but increases largely during the post-thymic development of the peripheral T cell pool. The hypothesis is not biased in respect to the underlying germ line repertoire of V genes, and is in fact compatible with the simple assumption that T and B cells use the same sets of V genes.

Generation of virus specific cytotoxic T cells in vitro. III. Spleen cells stimulated by viral antigens generate alloreactive cytotoxic T cells

Cytotoxic T lymphocytes (CTL) from DBA/2 strain mice primed with Sendai virus (SV) in vivo were activated by secondary stimulation of spleen cells with viral antigens in vitro and analyzed for their target antigen specificity. These effector cells lysed syngeneic Sendai virus infected target cells, marginally a variety of non-infected targets and had a strong cytotoxic effect on H-2b targets. Studies on the antigenic requirements revealed that all SV preparations which generated specific CTL also induced the alloreactive populations. Similar results were found in the response to Newcastle disease virus (NDV) and some influenza A viruses; all these viruses were mitogenic for lymphocytes. Experiments on the cellular requirements indicated that virus specific and alloreactive cells can be separated by their requirements for help and for restimulation. By competition experiments both activities could be attributed to clearly separable T cell subpopulations. The induction mechanism of alloreactive T cells by viral antigens is discussed.