Human leucocyte responses in vitro. I. Transformation of purified T lymphocytes with and without addition of partially purified monocytes.

Highly purified Fc receptor-negative T lymphocytes were obtained by filtration of human blood mononuclear cells through Ig–anti-Ig columns. Monocyte-enriched cells were isolated by density centrifugation in bovine serum albumin solutions. The proliferative response of the purified T lymphocytes was investigated with and without the addition of monocyte-enriched cells, after stimulation by allogeneic cells, phytohaemagglutinin (PHA), pokeweed mitogen (PWM), purified protein derivative (PPD), and tetanus toxoid. The results were as follows: (1) Fc receptor-negative T lymphocytes respond autonomously, and are the main source of proliferative cells found after stimulation by allogeneic cells and optimal doses of PHA, PWM and PPD. Addition of monocyte-enriched cells increases the responses, presumably by a non-specific feeder-effect in the cultures. (2) Stimulation of Fc receptor-negative T lymphocytes by and tetanus toxoid requires the presence of autologous monocytes in the cultures, whereas allogeneic monocytes do not support the responses. (3) Fc receptor-negative T lymphocytes are the main proliferating cells found after stimulation by , whereas other cells (B-lymphocytes and/or Fc receptor-positive T lymphocytes) may be responsible for a substantial part of the proliferation elicited by and tetanus toxoid. (4) Fc receptor-negative T lymphocytes can stimulate allogeneic cells in mixed lymphocyte culture, but monocyte-enriched cells and unfractionated mononuclear cells are better in this respect.