Immunocompetent Cells in the Blood of Immunized Chickens

INTRODUCTION ANTIGEN stimulation initiates the production of specific antibody that reaches a peak concentration in the blood several days later. Concomittant with the antibody response are characteristic histological changes in the activated lymphoid tissues, the proliferation of lymphocytes and differentiation of plasma cells (Leduc et al., 1955; Urso and Makinodan, 1963; Hanna et al., 1966). Direct correlation between the increase in antibody output and an increase in antibody-forming cells in the activated lymphoid organs of mammals have been clearly demonstrated with the agar plaque technic (Jerne et al., 1963) and the immunocytoadherence test (Biozzi et al., 1967). Adoptive immunity experiments have confirmed that spleen and lymph node of antigen-primed mammals contain cells capable of antibody synthesis in suitable hosts (Mitchison, 1957; Albright et al., 1964). Antigen stimulates immunological stem cells to proliferate and produce (a) populations of antibody-forming cells, and (b) reserves of immunologically activated precursors and memory cells which…