In vivo priming of mice with antigen and lipid A bestows proliferative ability on peritoneal exudate T cells in response to antigen or anti-αβ TCR antibody in the absence of macrophages in vitro: accessory function of NK cells

Abstract

Highly purified T cells of mice that have been primed in vivo with horse red blood cells (HRBC) and lipid A, but not with HRBC alone, can proliferate in vitro in response to HRBC or anti-αβ T cell receptor (TCR) antibody without macrophages. The mechanism of proliferation without macrophages was investigated. Mice were primed with HRBC and lipid A together or with HRBC alone 10 days in advance, and the peritoneal exudate cells (PEC) were obtained. Purified T cells were obtained by treating the PEC by the following series of procedures: nylon fiber column-passage, antibody (anti-Ia, anti-Mac-1, and LR-1) treatments with complement (C), and a G-10 column-passage. Cell proliferation was assessed by [3H]-thymidine (TdR) incorporation into the cultured T cells in response to HRBC or anti-αβ TCR antibody. The proliferation of T cells [T(HRBC+lipid A)] that had been prepared from the PEC of the mice primed with HRBC and lipid A increased dose-dependently to these stimulants, but T cells [T(HRBC)] prepared from PEC of mice primed with HRBC showed little or no proliferation in response to them. The expression pattern of a memory cell marker, CD44, on the cell surface of T(HRBC+lipid A) was obviously different from that on T(HRBC). The proliferation of T(HRBC+lipid A) was suppressed when the cells were cultured in the wells coated with hyaluronate, a ligand for CD44, or cultured after a previous treatment with anti-CD44 (IgG2a) and anti-IgG2a antibodies. In contrast, the proliferation of T(HRBC) was up-regulated in culture under the same conditions. Proliferative responses of T(HRBC+lipid A) to anti-αβ TCR antibody were enhanced in the wells coated with anti-CD28 antibody. These findings indicate that the proliferation of T(HRBC+lipid A) was not only supported by a stimulation of TCR but also regulated by another stimulation via ligands such as CD44 and CD28. The proliferation of T(HRBC+lipid A) was abolished when the cells were pretreated with AsGM1 antibody or anti-CD80 antibody and C. These findings indicate that the in vivo priming of mice with HRBC and lipid A generates a memory T cell population that is capable of proliferating without help of macrophages, but with NK cells, when stimulated their TCR.