We have previously described (1) a mouse IgG3 monoclonal antibody (AbR24) with a high degree of serological specificity for cultured human melanoma cells. All melanoma cell lines and two astrocytomas examined were positive for the heat-stable cell surface antigen detected by this antibody. Although choroidal melanocytes and brain had low levels of the antigen, a wide variety of other cells and tissues were unreactive. Three other monoclonal antibodies (Abs C5, I24, and K9), having a similar restricted specificity, were derived from the same fusion. These antibodies showed the same strong reactivity with melanomas and lack of reactivity with epithelial cells, but had a slightly wider specificity range in that they also reacted weakly with MOLT-4 (a T cell line), leukocytes, and some fetal tissues.In this communication, we identify the antigen detected by AbR24 as GD3, a previously characterized disialoganglioside.

An assay was developed to detect the cytotoxic effects of cytokines on rat pancreatic islet cells in monolayer culture. Cell lysis was detected by a 51Cr-release assay after 4 days of incubation with various cytokines. When tested alone, murine (rat and mouse) interferon-gamma (mIFN-gamma) produced a small dose-dependent lysis of islet cells; human IFN-gamma, mouse IFN-alpha/beta, interleukins 1 and 2 (IL-1 and IL-2), tumor necrosis factor (TNF), and lymphotoxin (LT) were inactive. When added together, the following combinations of cytokines showed synergistic cytotoxic effects: TNF (or LT) plus IL-1, TNF (or LT) plus mIFN-gamma, and IL-1 plus mIFN-gamma. These results indicate that the cytokine products of mononuclear cells of the immune system, IFN-gamma, TNF, LT, and IL-1 have strong synergistic cytotoxic effects on islet cells and therefore may act as direct chemical mediators of islet beta-cell destruction in type I (insulin-dependent) diabetes.

AH antigen was detected during our initial analysis of the humoral immune response of melanoma patients to autologous melanoma cells (I). Serum from patient AH was found to react with a cell surface antigen expressed by cultured autologous melanoma cells, but not by autologous skin fibroblasts or peripheral blood lymphocytes. Absorption tests indicated that AH antigen was expressed by some allogeneic melanoma cell lines, but not by any other normal or malignant cell types examined (1). An antigen with related properties was found during a comparable study of the autologous reactivity of sera from patients with astrocytoma (2). This antigen, A J, was expressed by all astrocytoma cell lines and a high proportion of melanoma cell lines, but was not detected on cultured fibroblasts or epithelial cancers. Comparison of the AJ and AH phenotypes of a series of melanoma cell lines showed only two phenotypes, AJ+/AH + or AJ-/AH-, suggesting a serological relatedness of AH and AJ antigens. Of the 75 patients with melanoma that have been analyzed for autologous reactivity, <5% have had demonstrable AH antibody in their sera (3). Overt cancer is not a prerequisite for the presence of AH antibody, because sera from 6 of 106 normal individuals were also found to have AH reactivity (4). In the present report, we summarize the results of typing an extensive panel of human cell types for AH antigen and provide evidence that the AH determinant is related to GD2 ~ ganglioside. Materials and MethodsCells and Tissues. The derivation and maintenance of melanoma and other cell lines are described in refs. 1, 2, 4-6. Noncuhured cells from autopsy specimens were prepared by finely mincing the specimen in RPMI 1640 medium supplemented with penicillin (100 IU/ml) and streptomycin (100 #g/ml); the resulting cell suspension was washed repeatedly in the same medium before use.

Recent observations suggest a role for interleukin-1 (IL-1), a polypeptide product of macrophage/monocytic cells, in the immune-mediated destruction of pancreatic islet beta-cells observed in type 1 diabetes. In this study, we investigated the effects of IL-1 on both alpha- and beta-cell secretory functions in rat islet cell monolayer cultures. Insulin release was 97% inhibited after 6 h of incubation in RPMI-1640 medium (11 mM glucose) containing 1 U/ml IL-1 and 96% inhibited after 24 h of incubation in medium containing 0.1 U/ml IL-1. The cell content of insulin in the monolayers was decreased by 66% (P less than 0.01) after 4 days of incubation in 10 U/ml IL-1; however, after a further 8-day incubation in IL-1-free medium, cell insulin content recovered fully. In contrast, cell glucagon content was decreased by 77% (P less than 0.001) after 4 days of incubation in 10 U/ml IL-1 and did not recover after a further 8-day incubation in IL-1-free medium. After an 18-h preincubation in medium with 0.1 and 1 U/ml IL-1, insulin release responses to 16.7 mM glucose were abolished in 4-h incubations, whereas responses to 0.1 mM 3-isobutyl-1-methylxanthine were normal, and after a further 2 and 5 days of incubation in IL-1-free medium, insulin responses to 16.7 mM glucose recovered fully. Similarly, the inhibitory effect of 16.7 mM glucose on glucagon release was lost after an 18-h preincubation in 0.1 and 1 U/ml IL-1, and did not recover fully after 2 and 5 days in IL-1-free medium, whereas the stimulatory effect of 3-isobutyl-1-methylxanthine on glucagon release was not affected by IL-1. We conclude that 1) IL-1 inhibits glucose-dependent and not cAMP-dependent mechanisms of insulin and glucagon release; 2) inhibition of glucose-stimulated insulin release by IL-1 is reversible, whereas the effect on glucose-modulated glucagon release is not; and 3) IL-1 causes a reversible decrease in the insulin content of islet cells and an irreversible decrease in glucagon content. These actions of IL-1 do not appear to account for the beta-cell-specific destruction of islets characteristic of type 1 diabetes.

We compared the cytotoxic effects to islet cells of lymphoid cells from diabetic and diabetes-resistant (DR) BioBreeding/Worcester (BB/W) rats with a 51Cr-release assay to detect lysis of normal rat islet cells. Splenic lymphoid cells from diabetic rats were more cytotoxic to islet cells (11.3 +/- 3.8%) than were lymphoid cells from DR rats (4.0 +/- 2.6%). This difference was amplified by incubating the lymphoid cells for 20 h with 5 micrograms/ml concanavalin A (ConA); islet cell lysis was 39.3 +/- 4.5% by ConA-activated diabetic cells and 9.6 +/- 2.7% by ConA-activated DR cells. The cytotoxic lymphoid cells were identified as natural killer (NK) cells, because treatment of diabetic lymphoid cells with anti-asialo GM1 serum and complement selectively removed a monoclonal antibody-defined subset of NK cells (OX8 +), and the NK-depleted lymphoid cells were not cytotoxic to either islet or NK-sensitive YAC-1 cells, even after culture with ConA. Of several lymphokine products of ConA-stimulated lymphoid cells, interleukin 2 (IL-2), but not interleukin 1 or interferon-gamma, significantly activated splenic lymphoid cells cytotoxic to islet cells, and the lymphoid cells from diabetic rats were more sensitive to IL-2 (3 U/ml) than were the cells from DR rats (30 U/ml). This study reveals the presence of ConA- and IL-2-responsive islet cytotoxic NK cells in the diabetic BB/W rat and suggests that IL-2 activation of NK cells may contribute to islet beta-cell destruction and diabetes in this animal.