CD3+ T lymphocytes expressing neither CD4 nor CD8 antigens exist in normal human peripheral blood in low frequency (approximately 3% of lymphocytes). The CD3+,4-,8- phenotype was stably maintained after in vitro culture in IL-2. Culture of CD3+,4-,8- cells in only rIL-2 generated cytotoxic T cells that lysed NK-sensitive and NK-insensitive tumor cell targets without MHC restriction. These experiments clearly show that phenotypically and functionally competent T cells expressing neither CD4 nor CD8 are present in normal peripheral blood.

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