Selection of B lymphocytes in the periphery is determined by the functional capacity of the B cell antigen receptor

Abstract

Within the B cell antigen receptor (BCR), the cytoplasmic tails of both Igα and Igβ are required for normal B cell development and maturation. To dissect the mechanisms by which each tail contributes to development in vivo, Igβ^–/– mice were reconstituted with retroviruses encoding either wild-type Igβ, an Igβ molecule lacking a cytoplasmic tail (Igβ^ΔC) or one in which the cytoplasmic tail was derived from Igα (Igβ^Cα). All constructs rescued B cell development and generated immature B cell populations in the bone marrow with similar expression levels of both Igβ and membrane-bound IgM. In the periphery, receptor-surface density was inversely proportional to the number of Igα tails in the BCR. Although peripheral-surface-receptor levels differed, splenic B cells expressing either Igβ or Igβ^Cα responded similarly to stimulation through the BCR. Analysis of membrane-bound IgM and Igβ expression revealed that peripheral-receptor expression was primarily determined by positive selection between the bone marrow and peripheral immature B cell populations. These data indicate that B cells are selected into the periphery on the basis of a common level of antigen responsiveness.

• signal transduction
• B cell differentiation
• CD antigen
• tyrosine kinase