Supernatant fluids from three human cultured cell lines, K562, NALM-1, and Daudi, all isolated from patients with lymphoreticular malignancies, were tested for suppressive activity toward normal lymphocytes in vitro. It was found that the K562 line elaborated material which effectively suppressed the response of normal human blood lymphocytes to the T-cell mitogens phytohemagglutinin and concanaval in A as well as the mixed lymphocyte reaction. Little or no suppressive activity was evident when supernatants from Daudi or NALM-1 were used. In contrast, a recent report [29] indicates that K562 does not inhibit the induction of immunoglobulin synthesis of B lymphocytes by pokeweed mitogen. The findings are discussed in the context of the immunosuppression associated with cancer and the apparent selective inhibition of different lymphocyte functions by material elaborated by different neoplasms.

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