Steinmuller, David

Abstract We have previously shown that murine epidermal cells (EC) from 5 H-2 compatible donor strains induce cytotoxic T lymphocytes (CTL) in C3H hosts that preferentially lyse donor EC as opposed to donor lymphoid cells (LC). This preference has been shown to be dependent on a single alloantigen disparity, designated epidermal alloantigen (Epa). In this report we studied the specificity of the CTL to determine whether Epa-antigens are in fact EC specific. Two populations of CTL could be identified by cross-immunization, cold-target inhibition, antigen-driven suicide, and limiting-dilution analyses. A minor CTL population recognizes alloantigens that are expressed by both EC and LC, but this population is necessary only for lysis of LC targets. The major CTL population is specific for Epa-antigens and reacts only with EC targets. At the induction phase of CTL responses, donor LC stimulators can weakly stimulate Epa-specific CTL, indicating LC populations express Epa-antigens in immunogenic form but at very low levels compared with EC. The preferential lysis of EC targets in these strain combinations can be attributed to the major Epa-specific CTL population, whereas lysis of LC targets is due to CTL specific for other alloantigens that are shared by EC and LC. The identification of CTL-activating, EC-specific alloantigens may help to explain the extreme immunogenicity of MHC compatible skin allografts.

Abstract Epidermal cells (EC) of AKR and CBA (H-2k) mouse strains share non-H-2 alloantigens that induce potent cytotoxic T lymphocytes (CTL) in H-2 compatible C3H hosts, and these CTL lyse EC targets in preference to lymphoid cell (LC) targets in H-2-restricted fashion in short-term cell-mediated cytotoxicity (CMC) assays. In contrast, C3H EC are not immunogenic in this regard in AKR and CBA hosts. (C3H × CBA)F1 hybrid hosts are nonresponders to AKR EC, exactly like the CBA parent strain hosts, and their own EC are immunogenic in C3H hosts and susceptible to lysis by the CTL so generated. Hence, CBA mice express a non–H-2 CMC determinant on EC that is absent on C3H EC. Offspring produced by backcrossing (C3H × CBA)F1 hybrids to the antigen-negative C3H parent strain were tested individually for their responsiveness to AKR EC immunogens and for the susceptibility of their own EC to lysis by C3H anti-AKR EC effectors. There was a clear 1: 1 distribution of the backcross offspring into 2 populations in both test systems. Moreover, responsiveness and antigenicity were inversely correlated in individual mice. Thus, the expression of EC alloantigens in the segregating offspring depends on the activity of genes at a single Mendelian locus. These results are most compatible with the hypothesis that a loss mutation occurred early in the history of the C3H strain at a non-H-2 locus that specifies a system of alloantigens expressed preferentially on EC. The finding that CTL generated by AKR EC immunogens in C3H/Heston and C3H/Andervont mice exhibit the same preferential lysis of EC as opposed to LC targets is consistent with this hypothesis because these C3H strains separated over 40 yr ago. Because this locus does not appear to correspond to any known locus, we have provisionally designated it the Epa (epidermal alloantigen) locus.

Abstract Epidermal cells (EC) obtained by trypsinization of tail skin of H-2k haplotype mouse strains AKR, B10.BR, B10.K, CBA, C3H, and RF were used as stimulators and targets of cell-mediated cytotoxicity (CMC) in 3-hour chromium-release assays. Host splenic effector cells were generated by priming mice with an injection of EC and boosting in mixed culture with irradiated donor-strain EC stimulators; then assayed for CMC towards donorstrain EC and lymphoid cell (LC) targets. When C3H is the donor strain and any of the other strains the host, little CMC is registered with EC targets. However, when C3H is the host and any of the other strains the donor, the CMC registered with donor-strain EC targets invariably is greater than that registered with LC targets, even with mitogen-induced lymphoblasts, indicating that C3H mice respond to non-H-2 alloantigens preferentially expressed by EC. The CMC evoked in C3H hosts by EC from any of the other other H-2k strains cross-reacts with EC targets from all of them, indicating extensive sharing of target-cell determinants. However, the CMC is H-2 restricted, and mapping tests with recombinant lines on the C57BL/10 background proved that the restriction depends on antigens mapping in the K region of the H-2 complex. T cell elimination tests indicate that the effector cells in these reactions are cytotoxic T lymphocytes. Moreover, tests conducted with medium supplemented with adult mouse serum instead of fetal calf serum indicate that the reactions are not dependent on xenogeneic serum but represent true examples of H-2-restricted CMC directed towards non-H-2 alloantigens expressed preferentially on EC.

Summary The eosinophil major basic protein (MBP) damages cells including those from organs whose dysfunction is associated with eosinophil infiltration. Concentrations of MBP in the toxic range were found in sputa from asthmatics, in pleural fluid and in sera. These findings suggest the hypothesis that the eosinophil produces damage to cells in disease.