Phenotype and topography of human thymic B cells. An immunohistologic study.
Using single and double labeling immunohistochemical techniques and a large panel of monoclonal antibodies against B-cell differentiation antigens, including those newly defined at the Fourth International Leucocyte Typing Workshop, we have examined the immunophenotype and tissue distribution of human thymic B-cells. The existence of a distinct B-cell population as a constant constituent of the thymic microenvironment has been noted only recently. We found a significant population of B-lymphocytes in the thymic medulla expressing the B-cell restricted antigens CD19, CD20, CD22, CD37, CD72, CD76 and IgM and IgD. As with other extrafollicular B-lymphocytes, they differ significantly from both follicle mantle and germinal center cells in morphology and immunophenotype, which points to alternative modes of B-cell differentiation. Thymic B-cells themselves show considerable heterogeneity and a subpopulation with dendritic features and the expression of CD23 has been referred to as "asteroid" cells. Their close association with T-cells and medullary epithelial cells points to a functional role for B-cells in the thymus. A second population of B-lymphocytes together with frequent lymph follicles is found within the extrathymic perviascular space. Though separated from the medulla by a layer of epithelial cells, a clear distinction between the B-cells of these two compartments is not always possible. The intramedullary B-cell compartment shows a parallel numeric increase with the occurrence of germinal centers in the perivascular space, mostly due to an accumulation of B-cells in the medulla adjacent to these lymph follicles. Thus a close relationship between the intra- and extramedullary B-cell population of the thymus seems likely.
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Medizinische Universitätsklinik, Abteilung für Hämatologie und Onkologie, Innsbruck, Austria.
Nachbaur
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D
Oberwasserlechner
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F
Kreczy
A
A
Huber
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H
Müller-Hermelink
H K
HK
D000293:Adolescent; D015703:Antigens, CD / Q000032:analysis; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis*; D001402:B-Lymphocytes / Q000737:chemistry*; D002648:Child; D005333:Fetus / Q000196:embryology; D006801:Humans; D007124:Immunoenzyme Techniques; D007072:Immunoglobulin D / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D007223:Infant; D010641:Phenotype; D013950:Thymus Gland / Q000166:cytology* / Q000196:embryology
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D007072:Immunoglobulin D; D007074:Immunoglobulin G; D007075:Immunoglobulin M