[Cellular interactions in the lymphocyte response to PHA in old people]

Peripheral blood lymphocytes (PBL) from the same number of old subjects (OS) and young subjects (YS) have been separated into subpopulations of T cells (T1 and T2 fractions) and B cells. Phagocytes were removed by carbonyl iron. The recovery in T1 is reduced in the OS. Their PHA response is inhibited by monocytes but not by polynuclears (PN). The response of their peripheral T cells is not reduced but it is not enhanced by adding PN. There is a normal T-B cell interaction in the response to PHA. It is suggested that the impaired PBL response to mitogens is secondary to the reduction of their content in T1 lymphocytes.