Germinal Center Cells: Antigen Specificity, Heavy Chain Class Expression and Evidence of Memory

Abstract

Germinal centers arise as discrete sites of B-cell differentiation in B cell areas of lymphoid tissue after antigenic stimulation. In the mouse germinal center cells can be confidently identified in cell suspensions as PNA^hi B cells, binding 10–30 times as much PNA as other B and T cells or plasma cells (PNA^lo) and are furthermore characterized by a lack of surface IgD^1–3. In Peyer’s patches the majority of germinal center cells bear the IgA isotype whereas in lymph nodes the predominant isotype after primary stimulation is IgM^2,3. Surface IgG expression was observed after secondary stimulation of the lymph nodes, suggesting an important role for the germinal center in heavy chain class switching². The germinal center population contains the majority of antigen-binding cells² and in a study on the localization of germinal center cells it has been demonstrated that they lack normal migratory and homing mechanisms most small lymphocytes possess⁴. Using two color FACS analysis we studied the stages in germinal center development and looked at the memory potential of these cells using an adoptive transfer system.