Search

Germinal center formation in the spleen of immunized, intact chickens was found to be an age-dependent phenomenon. Generation of germinal centers was at a maximum at the age of 4–5 weeks, which is the time of maximal size of the bursa of Fabricius. Thereafter, a rapid decline occurs. Age-dependence was most clearly demonstrated if autopsies were carried out 5 days after a second antigenic stimulation. Although germinal centers were found in the spleen of 20-month-old chickens 10–20 days after immunization, they appeared at a slower rate and to a lesser extent than in young chickens (4.5 weeks). An analogous finding was made after transplantation of mature postbursal cells into cyclophosphamide-treated chicks. These cells, taken from 10-week-old donors, were able to restore the production of germinal centers in the recipients, but not to the same extent and at the same rate as found after transplantation of bursal stem cells taken from 3-day-old donors. Only a few germinal centers were found in the lymphoid tissue of the cecal tonsil of intact, immunized chickens during the newly-hatched period. Later in life, no influence of age in the germinal center formation in the cecal tonsil was observed.