The studies aimed at presenting dynamic alterations in levels of lymphocytes T (receptor CD5+), Th (receptor CD4+), Tc/Ts (receptor CD8+), B (receptor IgM) and of lymphocytes with CD25+ receptor in rabbits immunized with Chlamydophila psittaci – strain 6BC. Serological studies were also conducted to detect presence of specific anti-Chlamydophila antibodies. Analysis of the results demonstrated that immunization of rabbits with the studied antigen resulted in an increase in levels of lymphocytes B in days 14, 28, 42, 49, 56, lymphocytes with CD25 receptor in days 14, 42, 49, lymphocytes T in days 14 and 35, Tc/Ts cells in days 28 and 35 and decreased levels of lymphocytes Th in days 7, 14 and 56, lymphocytes T in days 7, 42 and 49, lymphocytes Tc/Ts in the day 42 and lymphocytes with CD25 receptor in the day 21. On the other hand, positive titres of specific antibodies were detected in days 49-56 following immunization, i.e. 5-6 weeks later than the first significant alterations in levels of lymphocytes and of their subpopulations.