Human marginal zone B cells are not an activated B cell subset: strong expression of CD21 as a putative mediator for rapid B cell activation.
In the human spleen the marginal zone (MZ) contains medium-sized B cells with a distinct immunophenotype. A main function attributed to the MZ is its involvement in the primary response to blood-borne antigens, in particular to thymus-independent antigens type 2. In this study the presence of antigens related to activation and proliferation was evaluated in human spleens by immunohistochemical staining. It appeared that MZ B cells do not show interleukin 2 receptor expression, and are in G0 phase of the cell cycle, as demonstrated by the lack of Ki-67 reactivity. The most interesting finding is the high CD21 expression by MZ B cells in the absence of IgD expression. As the CD21 antigen has been shown to be involved in B cell activation in close linkage with IgM, it can be suggested that MZ B cells are particularly well equipped for rapid and easy activation in a primary immune response.
Timens
W
W
Department of Pathology, University of Groningen, The Netherlands.
Boes
A
A
Poppema
S
S
D015703:Antigens, CD / Q000032:analysis / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology*; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D011951:Receptors, Complement / Q000502:physiology*; D017464:Receptors, Complement 3d; D013154:Spleen / Q000166:cytology*
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D011951:Receptors, Complement; D017464:Receptors, Complement 3d