Significant frequency of cytotoxic T lymphocyte precursor cells specific for TNP-modified allogeneic cells in normal lymphocytes

Untreated or drug-treated tumor cells are differentially recognized by allogeneic lymphocytes

Murine tumor cells treated with triazene compounds (TZC), in vivo or in vitro, are capable of eliciting specific transplantation resistance in syngeneic hosts, and T-cell-mediated proliferative and cytotoxic responses, directed against novel drug-induced antigen(s). Since this phenomenon, referred to as chemical xenogenization (CX) could open up new perspectives in the immunochemotherapy of human neoplasias, it was of interest to investigate whether CX could also occur in human tumors. However, established human tumor cell lines along with fully immunocompetent autologous lymphocytes, are seldom available. Therefore studies were carried out to test whether parental or TZC-treated tumor cells could be differentially recognized by allogeneic lymphocytes. Experiments were performed in both human and murine models, using a lung adenocarcinoma line treated in vitro with TZC, or an established xenogenized mouse lymphoma, respectively. The results indicate that allogeneic cytotoxic T-lymphocytes (CTL) recognize specifically murine TZC-treated tumor cells. This was supported by the finding that antisera directed against the drug-treated cells abrogated the generation and the cytolytic activity of allogeneic CTL reactive against the TZC-treated tumor. In addition it was found that changes of the antigenic pattern of cell membrane recognizable by cloned allogeneic CTL occur in the TZC-treated human carcinoma cell line.

Manifestation of allo H-2-restriction specificity by self H-2-restricted T cells

Previous study has demonstrated that a considerable number of antigen-specific, allo H-2-restricted CTLPs could be recovered from normal lymphocytes. Experiments were conducted to examine whether antigen-specific, self H-2-restricted T cells could also manifest allo H-2-restriction specificity. Non-H-2-specific, self H-2-restricted CTLs were induced in the microcultures with a limited number of responder spleen cells from B10(H-2b) mice that had been primed with C3H.SW(H-2b) spleen cells. Two hundred thirteen non-H-2-specific CTLs generated in limiting dilution culture condition were assayed for cross-reactivity against TNP-modified and unmodified allogeneic targets of 10 different H-2 haplotypes. Of these CTLs, 29 (14%) were cross-reactive to a TNP-modified allogeneic target and seventeen (8%) to an unmodified allogeneic target. The quantitative analysis for cross-reactivity of non-H-2 specific, self H-2-restricted CTLs reveals a significant number of CTLs that were cross-reactive with either alloantigen or antigen (TNP) plus allo H-2. Furthermore, CTL clones with triple specificities including self H-2-restriction specificity, allo-reactivity, and allo H-2 restriction specificity were also found. These results indicate that antigen-specific, allo H-2-restricted T cells are distinct not only from alloreactive T cells but also from antigen-specific, self H-2-restricted T cells. Significance of the manifestation of allo H-2 restriction specificity by self H-2-restricted T cells is discussed in regard to the generation of T cell repertoire.

Growth-dependent variation of major histocompatibility complex (MHC) restriction and expression of Ly-2 and CD3/alpha/beta T cell receptor in cloned cytotoxic T cells

The specificity of major histocompatibility complex (MHC)-restricted antigen recognition by cytotoxic T cells (CTL) has been clearly correlated to the alpha/beta T cell receptor (TcR) complex on the T cell surface. Occasional changes in the specificity of in vitro cultivated CTL clones, therefore, have been suspected to result from alterations of the genes coding for the TcR alpha and/or beta chain. Here we demonstrate that pronounced variations in the stringency of MHC restriction, previously reported to occur during long-term culture of 2,4,6-trinitrophenyl (TNP)-specific CTL clones, may occur rapidly in a growth-dependent, reversible manner, i.e. without structural TcR variation. Several H-2b TNP-specific CTL clones were shown to possess strong cross-reactivity for H-2k TNP target cells when seeded at low cell numbers, but exhibit reduced or undetectable cross-reaction to H-2k TNP in high-density cultures. Another clone revealed "heteroclitic" properties with significantly stronger cytotoxic activity towards allogeneic (H-2k) than syngeneic (H-2b) TNP-modified target cells. In this case dilute cultures appeared as exclusively allo-MHC restricted, whereas dense cultures were allo/self cross-restricted. In all instances these phenomena were accompanied by cell density-dependent quantitative changes in the expression of Ly-2 and T cell antigen receptor. CTL from dilute cultures had at least 2-fold higher surface concentrations of Ly-2 and CD3 antigens than cells from dense cultures while other surface markers such as Thy-1 or LFA-1 were completely identical. No such effects were observed for CTL clones exhibiting cell density-independent specificity patterns. We conclude from these findings that (a) the stringency of MHC restriction specificity may be significantly affected by the amount of expressed TcR and/or Ly-2 molecules, (b) CTL possess mechanisms to regulate Ly-2 and TcR expression and, hence, their MHC-restricted antigen recognition, and (c) the ability to regulate Ly-2 and TcR expression may be altered during prolonged culture of a CTL clone.

Induction of anomalous killing activity from antigen-specific CTL clones by adding high doses of human recombinant interleukin 2

Four out of six long-term murine cytotoxic T lymphocyte (CTL) clones specific for trinitrophenyl (TNP)-modified spleen cells could develop an anomalous cytotoxicity against syngeneic and allogeneic tumor cells upon stimulation with TNP-modified spleen cells and high doses of human recombinant interleukin 2 (rIL-2). On FACS analysis, hyperactivated CTLs were positive for Thy-1, Ly 2 and LFA-1, but negative for L3T4 and asialo GM1. The staining profile of the cells with each antibody indicated that the CTL clones consisted of just one cell type. Monoclonal anti-Ly 2.2 and anti-LAA (lymphokine-activated cell-associated antigen) antibodies inhibited cytolysis of CTL and hyperactivated CTL clones against TNP-modified spleen cells, but failed to inhibit the anomalous killing of the hyperactivated CTL. The cold target competition test suggested the degeneracy of antigen specificity. The present study demonstrated that the CTL clone acquired a new specificity for tumor target cells upon stimulation with a high dose of rIL-2.