Migratory patterns of B lymphocytes. V. Surface Ig and migration properties of density gradient‐separated bursa cells

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Abstract
A study was made of bovine serum albumin density gradient-separated bursa cells with respect to their distribution on the gradients, % cytotoxicity with anti-Ig + complement (C) or anti-μ + C, and localization of fractions in irradiated syngeneic recipients. Layer A showed a higher cytotoxicity with anti-Ig + C or anti-μ + C than the others; layer D showed the lowest % cytotoxicity, although a large % of the cells not killed by anti-Ig were killed by anti-bursa serum + C. The C + D layers contained a much larger fraction of the Ig+ cells from the bursa in the 1–4-week-old than in the 6–12-week-old animals, suggesting a relative shift towards lower density of Ig+ bursa cells with age. When [3H]adenosine-labeled bursa cells from density gradient fractions were transferred, the % injected radioactivity found in recipient spleens was higher for fractions A and B than for fraction C + D. While 50–60 % of the cells from fractions A and B which localized in spleen were found in germinal centers and follicles, a much lower % of the cells from fraction C + D seen in spleen localized in these areas. The results were in agreement with those of previous studies suggesting that it is primarily the Ig-bearing population among bursa cells which localizes in follicles.