Helper activity of T lymphocytes which have been stimulated by keyhole limpet haemocyanin in vitro.

Details are given of a system for keyhole limpet haemocyanin (KLH)-induced DNA synthesis by murine T lymphocytes in vitro. Lymph node T cells from mice primed with KLH and Bordetella pertussis were stimulated with KLH under the defined conditions, and it was found that such cultured cells exhibited substantial non-specific helper activity. In contrast similarly primed T cells which had not been cultured showed only antigen-specific help. It is concluded that proper account should be taken of non-specific effects when studying the activity of antigen-specific helper cells in in vitro.