[Natural cytotoxic activity in different experimental conditions in hamsters (author's transl)]

Lymphoid cells from normal hamsters from our inbred Z strain were evaluated for their natural cytotoxic activity against YAC cells (mouse lymphoma) and ZDc125 and EHB cells (cultured syngeneic hamster fibroblasts) employing the 51Cr-release cytotoxic essay. Natural cytotoxic reactivity was high in spleen, intermediate in peritoneal cells and very low in the thymus. Natural cytotoxic response was present in newborn animals, reaches a maximal level within 4-8 months and declines very slowly thereafter. Treatment of hamsters with a single dose of cyclophosphamide (Cy) augmented the natural cytotoxic reactivity 2 to 3 days after injection; this activity was suppressed thereafter and reappeared 20-25 days after the Cy injection. Growth of transplantable ZDc125 or EHB tumour in syngeneic hamsters inhibited the natural cytotoxic activity as soon as the tumour was palpable. Preincubation of target cells in sera of tumour-bearing animals diminished the level of natural cytotoxic activity of spleen lymphoid cells. One can postulate that this could be due to the presence of antibodies or immune complexes in those sera.