IQI JIC MICE HAVE THYMIC B-CELLS

The thymus of IQI/Jic mice aged 3 to 15 months was studied chronologic ally by flow cytometry and immunohistochemistry. Thymic B cells (Thy B ) expressing the surface marker B220+IgM+ were detected in both sexes, but were more prominent in females. Thy B appeared as early as 4 mont hs of age in female mice, and the incidence of Thy B-positive mice and average Thy B ratio in thymocytes increased with age, reaching over 9 0% and 15%, respectively, after 9 months of age. In males, Thy B-posit ive animals appeared around 9 months of age and its incidence and aver age ratio increased gradually to 53% and 5%, respectively, at 15 month s. The Thy B-rich thymus was thickened with cortical atrophy and medul lary hyperplasia. Small- to medium-sized Thy B crowded and often forme d follicle-like structures in the medulla. When mice of various ages w ere injected with mercuric chloride to induce antinucleolar antibody, many Thy B-rich animals could not develop the antibody, implying that these animals are immunologically impaired. IQI/Jic can be a novel str ain to elucidate the relationship between the presence of Thy B and di sorders of the immune system.