Cell-mediated immunity to tumor cells

Leukocyte adherence inhibition and specific immunoreactivity in malignant melanoma

The leukocyte adherence inhibition (LAI) test has been used to assess specific anti-tumour immunoreactivity in 80 patients with malignant melanoma, 21 of whom had apparently been successfully treated by surgery, and 44 control subjects. Reaction with melanoma extracts in vitro enabled the activity of blood leukocytes to be detected by inhibition of their adherence to glass, while serum was tested for factors which modified this inhibition. Of the patients with tumours (ranging from primary melanoma in situ to advanced disseminated disease), 22/24 had active leukocytes and 50/58 has serum blocking factor; two of the sera, from patients with regressing tumours were unblocking. After surgery with no clinical recurrence, leukocytes continued to be active except when tested several years after operation. Blocking factor rapidly disappeared in 16/20 patients tested, and in several patients examined serially the serum became unblocking. In three cases, persistence of serum blocking was followed by clinical diagnosis of metastases. Leukocyte activity was nerver detected in control subjects (0/10), many of whom had other kinds of tumours or skin lesions. Blocking activity in serum was found in only 3/38 controls with no history of melanoma (1 had a fibrosing cellular blue naevus and 2 had liver disease). Thus the LAI test correlated well with clinical and pathological findings, and shows great promise for the reliable, rapid and specific immunodiagnosis of malignant melanoma.

Inhibition of T-lymphocyte-mediated tumor-specific lysis by alloantisera directed against the H-2 serological specificities of the tumor

After appropriate in vivo or in vitro immunization, cytotoxic T lymphocytes (CTL) are generated which efficiently kill cells bearing particular membrane antigens in common with the immunizing cell (reviewed in reference 1). Such CTL have been most thoroughly studied in mice, employing alloimmunization with cells differing at the major histocompatibility locus, H-2. in such cases, the predominant cell surface antigens recognized by the CTL appear to be the molecules carrying the serologically defined H-2 specificities, coded for by the K and D regions of the H-2 complex (2). In other syngeneic models of cell-mediated specific cytolysis, involving lymphocyte chariomeningitis (LCM) virus- or ectromelia virus-infected cells or TNP-modified lymphoid cells, thymus-derived cells also constitute the main effector cell type. The CTL generated in these latter systems function most efficiently when virus-infected or TNP-modified target cells share identitites at the H-2K or H-2D loci with the effector CTL and stimulator cells (3-5). Another set of experimental systems in which CTL are generated and play a significant biological role is that of immunity to tumor-associated antigens (TAA) (6). The nature of the TAA which the CTL recognize is only beginning to be understood. Several recent reports indicated the existence of physiochemical and/or antigenic relationships between TAA and H-2 antigens (7,8). These relationships, together with the genetic restrictions cited above in the generation of CTL involving products of the H-2K or H-2D loci suggested the possibility that in certain tumor systems, the TAA which are able to most effectively stimulate CTL responses might be structurally similar to, or linked with, the H-2K or H- 2D molecules on the tumor surface. It has been previously demonstrated in allogenic models that antisera specific for the appropriate H-2K or H-2D products present on a target cell could specifically block CTL-mediated lysis (1,9). This report demonstrates that certain anti-H-2 alloantisera specific for the target tumor cells can block lysis of those target cells mediated by syngeneic tumor-specific CTL effector cells.

Inhibition of in vitro lymphoproliferative responses to tumor-associated antigens by suppressor cells from rats bearing progressively growing Gross leukemia virus-induced tumors

W/Fu rats were injected subcutaneously with low numbers of cells from the Gross leukemia virus-induced lymphoma, (C58NT)D, which induced transient tumor growth and regression (regressors), or with high numbers of tumor cells resulting in progressive tumor growth (progressors). Spleen cells from regressors had a significant reactivity in the mixed leukocyte tumor cell interation (MLTI), while spleen cells from progressors were unresponsive. Similarly, the responses to the non-specific mitogens, phytohemagglutinin and concanavalin A, were suppressed in spleen-cell cultures of progressors. Passage of spleen cells from progressors over rayon adherence columns or pretreatment with an iron/magnet technique resulted in almost complete restoration of MLTI and mitogen responses. Addition of spleen cells from progressors depressed the MLTI of spleen cells from regressors and the mitogen reactivity of normal spleen cells. Serum from progressors also suppressed MLTI and mitogen reactivity. These data indicate that, in spleens of rats bearing progressively growing tumors, suppressor cells can be demonstrated which inhibit specific reactivity to tumor-associated antigens and non-specific reactivity to mitogens. The presence of suppressor cells or of inhibitory factors in the serum may contribute to the immunosuppression frequently observed in tumor-bearing hosts.

Restoration of specific immunity against SV40 tumor-specific transplantation antigen to lymphoid cells from tumor-bearing mice

Specific cell-mediated immunity to SV40 tumor-specific transplantation antigen (TSTA) in BALB/c mice undergoing progressive tumorigenesis by syngeneic SV40-transformed cells (VLM) was investigated in vivo using a tumor-cell neutralization test. Specific cellular reactivity to SV40 TSTA was not detected in BALB/c mice bearing large tumors (10-15 mm mean diameter) but was demonstrable after tumor excision. Specific cytotoxic reactivity against syngeneic SV40-transformed cells in vivo could be restored to lymphoid cells from VLM tumor-bearing mice either by culturing the lymphoid cells in vitro or by treating them with papain or trypsin. Enzyme-treated lymphoid cells from MCA tumor-bearing BALB/c mice had no cytotoxic reactivity against VLM cells. These studies suggest that tumor-bearing hosts possess lymphocytes which are sensitized to the TSTA of the tumor but that the reactivity of these lymphocytes is blocked.

Lysis of leukemia cells by spleen cells of normal mice

Spleen cells from 2- to 3-month-old normal mice of some strains having a low incidence of spontaneous leukemia were found to lyse cells of the spontaneous AKR leukemia K36 in the 51Cr release assay. Incubation of 51Cr-labeled ADR K36 cells with spleen cells from normal C57BL/6, C57L, C57BL/10, and RF mice resulted in the release of significantly more 51Cr than that released in the presence of medium alone. In contrast, 51Cr released from AKR K36 cells after incubation with spleen cells from mice of the high leukemic strains AKR and C58 was less than that released spontaneously. The results of competitive inhibition tests when C57BL/6 spleen cells were incubated simultaneously with 51Cr-labeled AKR K36 target cells and varying numbers of nonlabeled cells demonstrated that the cytotoxic activity of normal C57BL/6 spleen cells was directed against an antigen(s) associated with several leukemias, but that was undetectable on normal thymocytes. Pretreatment of C57BL/6 spleen cells with carbonyl iron and a magnet, which removed phagocytic macrophages, did not decrease the cytotoxic acitivity for AKR K36 cells.

Identity and cytotoxic capacity of cells infiltrating renal allografts

To determine the identity and cytotoxic capacity of lymphoid cells involved in allograft rejection, we studied viable, monodispersed cells recovered from 10 rejected human renal allografts. A heterogeneous population of cells including macrophages and both bone-marrow (B) and thymus-derived (T) lymphocytes accumulate in rejected grafts. Infiltrating lymphocytes exerted a specific cytolytic effect on 51Cr-labeled peripheral blood lymphocytes bearing donor antigens, ranging from 7 to 44 per cent specific lysis in nine of 10 cases. Cytolysis was closely correlated (r equal 0.91, p less than 0.05) with the histologica grade of cellular rejection but not with humoral rejection, suggesting that cytotoxic lymphocytes are an important element in cellular rejection. Limited fractionation studies showed that both T cells (in early rejection) and non-T cells (in late rejection) may produce cytotoxicity. Since as many as 50 per cent of cells recovered bore Fc receptors, the rejection process may also involve antibody-dependent target-cell lysis.