Different anti-CD21 antibodies can be used to discriminate developmentally and functionally different subsets of B lymphocytes in circulation of pigs

Monoclonal antibodies IAH-CC51, BB6-11C9.6 and B-Ly4 are routinely used to detect CD21 orthologue on the surface of porcine B lymphocytes. Cross-reactive studies show that IAH-CC51 and B-Ly4 recognize only a portion of B cells that are positive for pan-specific BB6-11C9.6. This indicates that CD21 is always present on all mature B cells but can be expressed in at least two differential forms, and these were assigned as CD21a and CD21b. We used IAH-CC51 together with anti-CD2 to define four subpopulations of B cells. Ontogenetic and in vitro culture studies, analysis of cell size, expression of CD11b and class-switched phenotype together with measurement of proliferation and cell death, revealed that these subsets represent distinct populations. Phenotypic and functional features collectively suggest that CD21b+ B cells are less mature than CD21b−. The present work is the first to show that distinct subsets of mature B cells can express differential forms of CD21.

► Different anti-CD21 mAbs recognize different amount of mature B cells in swine.
► CD21 is always present on mature B cells but is expressed in differential forms.
► CD2/CD21 subsets of porcine B cells represent functionally different subpopulations.
► Porcine CD21b+ B cells are less mature than CD21b−.