Developing neonatal rabbit appendix, a primary lymphoid organ, is seeded by immature blood-borne B cells: evidence for roles for CD62L/PNAd, CCR7/CCL21, alpha4beta1 and LFA-1.
Young rabbit appendix is a homologue of chicken bursa of Fabricius; both are crucial sites for preimmune B-cell repertoire development. We describe here some of the molecules involved in the multi-step recruitment of blood-borne B cells into neonatal rabbit developing appendix. Sialyl-Lewis-x, CD62L and integrins such as LFA-1 and alpha4beta1 were detected on B cells in peripheral blood. Peripheral lymph node addressin (PNAd), a CD62L counter-receptor was observed on appendix HEV. We also detected chemokine receptor CCR7 on peripheral blood B cells and one of the CCR7 ligands, CCL21, on appendix HEV but not in appendix follicles. Higher levels of CXCR5 expression compared to CCR7 on appendix B cells suggest that CXCR5 may be involved in recruitment of B cells into follicles. The proportions of appendix B cells expressing CD62L, sialyl-Lewis-x and alpha4beta1 declined between day 3 and 4 weeks after birth while percentages of Lewis-x+ appendix B cells increased. These changes correlate with the stage of repertoire diversification by gene conversion in both rabbits and chickens. The cross-reactivity of antibodies to mouse or human adhesion molecules described in this study indicates that some of the structures of these important molecules are conserved across species.
Sinha
Rajesh K
RK
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institute of Heath, Building 10, Room 11N311, 10 Center Drive, MSC 1892, Bethesda, MD 20892, USA.
Mage
Rose G
RG
D000818:Animals; D001065:Appendix / Q000166:cytology / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002448:Cell Adhesion / Q000276:immunology; D039041:Integrin alpha4beta1 / Q000378:metabolism; D019041:L-Selectin / Q000097:blood / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000097:blood / Q000378:metabolism*; D011817:Rabbits; D054400:Receptors, CCR7; D019707:Receptors, Chemokine / Q000097:blood / Q000378:metabolism*
C515370:CCR7 protein, human; C515371:Ccr7 protein, mouse; D039041:Integrin alpha4beta1; D016169:Lymphocyte Function-Associated Antigen-1; D054400:Receptors, CCR7; D019707:Receptors, Chemokine; D019041:L-Selectin