Cell-mediated cytotoxicity (CTX) was studied in meningioma patients before and within 2 weeks of complete excision of the tumour, using the [3H]-prolin- microcytotoxicity test. Three of 7 patients tested before surgery showed specific CTX, 2 revealed a "non-specific" (tumour-unrelated) response, and 2 were non-reactive. After surgery, CTX decreased from 84 to 50% in one patient and became negative in 2 others previously positive. One of 2 patients showing "non-specific" CTX preoperatively became positive, while the other remained unchanged. All patients were receiving dexamethasone (DXM) at the time they were tested. Lymphocyte responses to PHA were not significantly different before or after surgery (i.e. after prolonged treatment with DXM), from healthy controls. Blocking activity could be detected in the sera of all 3 patients before surgery. This activity was not specific for meningiomas. Paradoxically, the same sera did not inhibit the proliferative response to PHA. Serum from only one patient consistently suppressed the blastogenic response of homologous lymphocytes to PHA. Inhibitory activity was associated with the IgG fraction of his serum.
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