Mucosal B Cell Differentiation and Regulation

• A prime function of the mucosal immune system is the production of secretory immunoglobulin (Ig) A antibodies. To initiate this, the organized lymphoid system is strategically located at sites where mucosal antigens are encountered. The follicle-associated epithelium (FAE) hosts specialized cells called M cells that effectively take up antigen. After transport of antigen via the FAE, the mucosal-associated lymphoid tissues (MALT) support the priming, propagation, and differentiation of naïve B and T cells. Activated B cells undergo class-switch recombination from IgM to IgA in MALT. As a consequence of extensive cell division in germinal centers, formed with the help of CD4 T cells, these cells acquire mutations in their V(D)J Ig genes. Somatic mutations diversify the specificities of the receptors, and this contributes to an enhanced antigen binding ability after selection of high-affinity variants. IgA B cells develop into memory cells and long-lived plasma cells, and through an intricate system of ligands and receptors most of the IgA cells home to the effector sites in the lamina propria of the nonorganized mucosal membranes. Long-lived plasma cells also reside in the bone marrow from where most of the serum IgA emanates. Despite many years of intense interest in the regulation of mucosal IgA B cell responses, several questions still remain unanswered. This chapter describes how IgA B cells are activated, distributed, and maintained as either long-lived plasma cells or memory B cells, and it reviews recent developments in the field. Knowledge about IgA B cell development is critical not only for mucosal vaccine development but also for our understanding of how homeostasis can be maintained between the host and the microbiota. © 2015 Elsevier Inc. All rights reserved.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Immunologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Immunology in the medical area (hsv//eng)

Nyckelord

Commensal flora

Germinal center

Gut plasma cells

Gut-associated lymphoid tissues

IgA B cell

IgA class switch recombination

Microbiota

Mucosa and B-1cells

Peyer's patches

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