Help and suppression by lymphoid cells as a function of cellular concentration.

Abstract

Phytohemagglutinin-stimulated uptake of [3H]thymidine in mixtures of human lymphocytes from the same source depended on cell concentration in vitro and on the cultivation period. Helper and suppressor effects were obtained by varying cell concentration and cultivation periods. The possibility that helper and suppressor subpopulations were responsible was avoided by mixing lymphoid cell line cells with others of the same monoclonal origin. Even under these conditions, the direction and the extent of activity depended on the same 2 variables. This weakened the case for postulating existence of distinct lymphocyte subpopulations with helper or suppressor properties. This case was based on use of damaging treatments believed to separate cell populations which were then found to differ in their helper and suppressor properties. The effect of such treatments may be mediated through changes in interacting cell concentrations. The function of lymphoid cells ascertained in 1 set of conditions need not apply within a different cellular environment.