Unique Aspects of Immunoglobulin Expression During Early B Cell Differentiation in the Chicken

Abstract

Perhaps the most significant events during the life history of B cells are changes in the expression of immunoglobulin genes. In this regard, results of studies in birds and mammals suggest that B cell development can be conveniently divided into 3 principle stages. The first is primarily concerned with the generation of clonal diversity; during this stage, non-Ig producing stem cells differentiate and divide to form large numbers of B lymphocytes, each expressing IgM antibodies of a single specificity. Next, the generation of isotype diversity occurs within B cell clones; limited numbers of cells within each clone switch from IgM synthesis only to the surface expression of other immunoglobulin classes without a change in antibody specificity (or V-region gene expression). Lastly, clones are selected for stimulation by antigen, or clones may be stimulated by polyclonal mitogens to divide and differentiate into plasma cells. Helper and suppressor T cells participate primarily in regulating the latter events.