Relationship between mitogenic factor and in vitro lymphocyte stimulation during guinea pig immune response to KLH.

Lymphocyte stimulation and production of the lymphokine mitogenic factor (MF) in response to specific in vitro challenge were studied in parallel using lymphocytes from animals sensitized with different doses of keyhole limpet haemocyanin at various times after sensitization. Overall, agreement between the two assays of cellular response was good. However, examination of the antigen dose-response characteristics in each experimental situation revealed dissociation in some cultures. Blood leucocyte responses developed later than those of lymph node cells. The latter gave good MF but were poorly stimulated at day 60, when both responses were maximal for blood leucocytes, indicating a possible redistribution of responsive cells from the nodes to the blood. Treatment of guinea pigs with cyclophosphamide affected lymphocyte stimulation to a greater extent than MF production. Only a part of the antigen-induced stimulation of lymph node cells could be attributed to MF elicited in culture.