Gamma delta T cells from influenza-infected mice develop a natural killer cell phenotype following culture.

Bronchoalveolar lavage (BAL) populations recovered from mice with secondary influenza pneumonia contain gamma delta T cell receptor (TCR)+NK1.1- lymphocytes and gamma delta TCR-NK1.1+ natural killer (NK) cell populations. Stimulating the CD4-8- component of the BAL with a monoclonal antibody to CD3 epsilon and rIL-2 leads to the emergence of substantial numbers of CD4-8- gamma delta TCR+NK1.1+ and CD4-8- alpha beta TCR+NK1.1+ lymphocytes. The NK1.1+ gamma delta T cells are potent cytotoxic effectors, causing much higher lysis of YAC-1 target cells than the gamma delta TCR+NK1.1- lymphocytes that are present concurrently. CD4+ and CD8+ alpha beta T cells cultured in the same way express little (if any) NK1.1. The possible functional role of NK1.1+ gamma delta T cells is discussed.