In Vivo Activated Lymphoid Cells (IVALC) Affect the Cloning Efficiency of Human T Lymphocytes Reactive to a Soluble Antigen, Purified Protein Derivative

Publisher Website
Google Scholar
Abstract
Peripheral blood mononuclear cells (PBMC) of normal individuals were found to contain a proportion (4-9%) of in vivo activated lymphoid cells (IVALC). The IVALC were characterized by their expression of interleukin 2 (IL-2) receptors, and by the ability of proliferate in the presence of exogenous IL-2. There was a good correlation between the proportion of IVALC in different cell populations and the level of cell proliferation to IL-2. It was found that IVALC isolated from autologous PBMC of Bacillus Calmette-Guerin (BCG)-immunized individuals contained no significant proportion of purified protein derivative (PPD)-reactive lymphocytes. The addition of IVALC markedly enhanced proliferative responses of the autologous T4+T8-IL-2 receptor-negative cell cultures to antigen stimulation. An increased proportion of activated (IL-2 receptor-positive) lymphocytes was generated in PBMC as compared to autologous T4+T8-IL-2 receptor negative cell cultures after stimulation with PPD. Limiting dilution analysis showed that IL-2 responsive IVALC through expansion markedly affected the cloning efficiency of antigen-proliferating T cells of autologous PPD-stimulated PBMC cultures. Only 1 out of every 11-25 blast cells generated in the PBMC cultures could establish itself as a growing colony based on determinations in six BCG-positive individuals. By using a T4+T8- population depleted of IVALC to generate PPD-reactive lymphocytes, a three- to four-fold increase in the cloning efficiency of antigen-specific cells was obtained.