"NK-like" T cytotoxicity against B lymphocytes in a hypogammaglobulinemic patient

Physiologically, cells with NK activity appear to exert a negative control on immunoglobulin production. The clinical association of large granular lymphocyte (LGL) proliferation with hypogammaglobulinemia suggests that these functional NK cells could also be involved in pathological situations. We studied in vitro lymphocyte functions in a patient presenting LGL proliferation associated with hypogammaglobulinemia. The CD3+ CD8+ CD57+ CD16- phenotype lymphocytes expressed a high NK type cytotoxicity towards K562 targets, suggesting that they may be considered as "NK-like" T cells. We cultured the patient peripheral blood mononuclear cells (PBMC) with control subject PBMC and with PBMC from two other subjects with B chronic lymphocytic leukemia (B-CLL) of the CD20+ CD21- CD10- phenotype. Patient PBMC exhibited a lytic activity on control PBMC and on the B lymphocytes of one of the two B- CLL but only in the presence of PWM. This activity was not exerted by the culture supernatant and required a cell-to-cell contact. We suggest that the hypogammaglobulinemia observed in this patient may be related to a cytotoxic effect exerted on B lymphocytes by a CD3+ CD8+ CD57+ CD16- LGL proliferation.