Plaque-forming cells in rabbits immunized with BCG bacilli.

Area of Science:

• Immunology
• Cellular immunology

Background:

• Tuberculosis (TB) is a significant global health challenge.
• Understanding the immune response to BCG vaccination is crucial for developing effective TB control strategies.

Purpose of the Study:

• To enumerate plaque-forming cells (PFC) in rabbits immunized with BCG.
• To analyze the kinetics of PFC production in the primary and secondary immune responses.
• To investigate the relationship between blast cell outflow and PFC production.

Main Methods:

• Rabbits were immunized with BCG.
• Plaque-forming cells (PFC) were enumerated using the localized hemolysis in gel assay.
• Sheep red blood cells coated with tuberculin protein were used as target cells.
• PFCs were quantified in the regional lymph node, efferent lymph, and spleen.

Main Results:

• In the primary response, maximal PFC production occurred at 5 days in the lymph node and 7 days in the spleen.
• Efferent lymphatic cells showed limited PFC numbers during the primary response.
• The secondary response exhibited sharp PFC peaks at 3 days in the lymph node, spleen, and efferent lymphatic cells.
• Blast cell outflow from the regional lymph node peaked at 3 days in both primary and secondary responses.

Conclusions:

• The secondary immune response to BCG is characterized by a rapid and robust increase in PFCs.
• Lymphatic cells play a role in the dissemination of immune cells during the secondary response.
• Blast cell outflow correlates with PFC production, suggesting its involvement in immune cell trafficking.