Heterogeneity of M-cell-associated B and T cells in human Peyer's patches.
The specialized M cells in the follicle-associated epithelium (FAE) of Peyer's patches (PP) represent an intimate interphase between luminal antigens and gut-associated lymphoid tissue (GALT). M cells form pockets that contain clusters of leucocytes probably involved in the first encounter with antigens from the gut lumen. Three-colour immunofluorescence in situ phenotyping of these leucocytes in humans revealed about equal numbers of B (CD19/20+) and T(CD3+) lymphocytes, the latter mainly CD4+ (median 73%, range 40-90%), but relatively few macrophages (CD68+). Most B cells (90%) were positive for surface IgM (sIgM) and often co-expressed sIgD (median 34%, range 6-60%). Occasional B cells (median 2%) did not express CD45RA (range 0-15%) and 13% virtually lacked HLA-DR (range 0-40%). Some B and T lymphocytes expressed the nuclear proliferation marker Ki-67 (range 1-10%). The M-cell pockets also contained occasional cells with cytoplasmic IgA or IgM. These sites thus contained a heterogeneous B-cell population with features of both follicular mantle (sIgD+ sIgM+) and marginal zone (sIgD- sIgM+) B lymphocytes. Adjacent T lymphocytes were generally of the memory phenotype (CD45RO+). Our findings suggest that the M-cell-associated B lymphocytes represent local extensions of B-cell follicles towards the gut lumen, developed topically to facilitate antigen presentation and diversification of mucosal immune responses.
Farstad
I N
IN
Laboratory for Immunohistochemistry and Immunopathology (LIIPAT), University of Oslo, National Hospital, Norway.
Halstensen
T S
TS
Fausa
O
O
Brandtzaeg
P
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002648:Child; D003108:Colonic Diseases / Q000276:immunology*; D004848:Epithelium / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007072:Immunoglobulin D / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007150:Immunohistochemistry; D007156:Immunologic Memory; D019394:Ki-67 Antigen; D017493:Leukocyte Common Antigens / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000276:immunology; D009687:Nuclear Proteins / Q000276:immunology; D010581:Peyer's Patches / Q000166:cytology / Q000276:immunology*; D010641:Phenotype; D013601:T-Lymphocytes / Q000276:immunology*
D015703:Antigens, CD; D007072:Immunoglobulin D; D007075:Immunoglobulin M; D019394:Ki-67 Antigen; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D017493:Leukocyte Common Antigens