title: Accumulation of CTLA-4 expressing T lymphocytes in the germinal centres of human lymphoid tissues.
abstract: CTLA-4, a coreceptor with sequence homology to CD28 is expressed on T cells after activation. Mice deficient for CTLA-4 die young from massive infiltration of many organs by activated T cells, which highlights the essential inhibitory role the coreceptor plays in the regulation of the immune response. To study the prevalence and distribution of CTLA-4 in situ immunohistological analyses were carried out on human tonsils and lymph nodes. Expression of CTLA-4 was restricted to alpha beta T cells, and CTLA-4+ B cells were not observed. In T-cell areas, 2-10% of T cells were positive for CTLA-4 with similar percentages in the CD4+ and CD8+ subpopulations. In the germinal centres (GC) the fraction of CTLA-4+ T cells was much higher (70-90%). This was due to frequent expression of CTLA-4 on the CD4+ helper subpopulation. GC CD8+ T cells were rare and mostly did not express the coreceptor. The CTLA-4+ T-cell fraction was also over-represented among intraepithelial tonsillar T cells. Cycling (Ki-67+) and apoptotic (TUNEL+) T cells were never positive for CTLA-4, while a subset of CD25+ cells did express the coreceptor. Since CTLA-4 is essential for the physiological limitation of the immune response, GC T cells, which are mostly CTLA-4 positive, might be important in this process.
authors.affiliation: Bernhard-Nocht-Institut für Tropenmedizin, Hamburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Castan
authors.forename: K
authors.initials: K
authors.lastname: Tenner-Racz
authors.forename: P
authors.initials: P
authors.lastname: Racz
authors.forename: B
authors.initials: B
authors.lastname: Fleischer
authors.forename: B M
authors.initials: BM
authors.lastname: Bröker
mesh_terms: D000069594:Abatacept; D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000032:analysis*; D017209:Apoptosis / Q000276:immunology; D060908:CTLA-4 Antigen; D002648:Child; D002675:Child, Preschool; D005260:Female; D005455:Fluorescent Antibody Technique; D018858:Germinal Center / Q000276:immunology*; D006801:Humans; D018796:Immunoconjugates; D007124:Immunoenzyme Techniques; D008198:Lymph Nodes / Q000276:immunology*; D008297:Male; D014066:Palatine Tonsil / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D000069594:Abatacept