Early Appearance of Sensitized Lymphocytes in Mice Infected with Listeria Monocytogenes

Abstract

These experiments were designed to detect the earliest appearance of cell-mediated immunity (CMI) in primary Listeria infection. Two lines of evidence suggested that CMI was operating by day 3 after infection. First, in the livers and spleens of mice treated with anti-thymocyte serum, a potent suppressor of CMI, bacterial numbers were similar to those in control mice for the first 2 days after primary infection, but were consistently higher on the 3rd, 4th, and 5th days. Second, spleen cells from Listeria-infected donors were capable of conferring an antibacterial effect on infected recipients if transferred 3, 4, or 5 days (but not 2 days) after donor infection. The full expression of the potency of the immune cells was ensured by culturing them in vitro for the 22 hr prior to transfer under conditions which virtually eliminated the large numbers of cell-associated viable Listeria remaining from the immunizing infection.