Antigen-selected, immunoglobulin-secreting cells persist in human spleen and bone marrow

Abstract

IntroductionPlasma cells (PCs) are terminally differentiated immunoglobulin (Ig)-secreting cells (ISCs) responsible for humoral immunity. [1][2][3] ISCs can arise from several differentiation pathways. During the extrafollicular reaction, some antigen (Ag)-specific naive B cells undergo rapid clonal expansion and differentiate into ISCs. 1,4,5 Many extrafollicular ISCs are short-lived and secrete either IgM or downstream isotypes. 6,7 The V H genes of extrafollicular ISCs typically remain in their germline configuration, 4,8 indicating they have not undergone significant somatic mutation. Naive B cells can also give rise to ISCs by way of the germinal center (GC) reaction. It is within GC that antigen-specific naive B cells undergo proliferation, somatic mutation of Ig V region genes, Ig isotype switching, and affinity maturation. 1,4,5 Antigen-selected GC B cells can differentiate into ISCs, 5,9,10 most of which migrate to the bone marrow (BM) and become long-lived PCs, whereas a small proportion remains in the spleen. 2,3,7,9,11,12 At the same time, some GC B cells develop into memory B cells, 4,5,10 which can subsequently yield ISCs directly after repeated exposure to an immunizing antigen. 13,14 Thus, the GC reaction serves to expand and diversify the B-cell repertoire, producing high-affinity variants for the long-term maintenance of protective immunity.Most studies examining PCs have been performed using spleens and BM from immunized rodents. However, for a complete understanding of human PC differentiation, and, more important, human diseases characterized by the expansion or transformation of ISCs, it is necessary to examine the human counterpart of these cells directly. Human ISCs can be identified by an up-regulation in expression of CD38 and a concomitant down-regulation of CD20. 15 Based on this phenotype, significant numbers have been detected in BM and peripheral blood (PB) 15,16 and in mucosa-associated lymphoid tissue such as tonsils and gut, [17][18][19] where they usually constitute a very small proportion of mononuclear cells (MNCs; less than 0.1%-1.0%). 15,17,20,21 Although ISCs in human tonsils, PB, and BM have been extensively characterized, 16,17,[20][21][22][23][24][25] ISCs in human spleen have not been reported. Given the identification of a population of long-lived murine splenic PCs, we hypothesized that an analogous population would exist in humans and that this population could contribute to the maintenance of long-term humoral immunity. In this paper we report the identification of a population of human splenic CD38 ϩϩ CD20 Ϯ cells that exhibited many characteristics of BM PCs, and we propose that these cells in human spleen represent an important population of ISCs. Identifying human splenic ISCs will contribute to our understanding of the role played by these cells in normal humoral immunity and of human diseases characterized by B-cell hyperactivity or deficiency. Materials and methods ReagentsThe following monoclonal antibodies (mAbs) were used in this study: fluorescein isothi...

Expansion of Functionally Immature Transitional B Cells Is Associated with Human-Immunodeficient States Characterized by Impaired Humoral Immunity

“…2). CD23 was on naive and transitional, but down-regulated on memory, cells, consistent with previous studies of naive and memory B cells present in human spleen and tonsils (13)(14)(15)32).…”

“…CD24 ϩ CD38 Ϫ B cells also expressed low but detectable levels of CD25, CD80, CD86, and CD95 ( Fig. 2), again consistent with the phenotype of memory B cells in human spleen and tonsils (13,14,32). The adhesion molecule CD44 (Fig.…”

“…The V H 5 genes were amplified from cDNA prepared from sorted B cells by nested PCR as previously described (32). Nucleotide sequences were analyzed using the Sequencher version 4.5 program (Gene Codes), and comparisons were performed using the GenBank database.…”

“…Expression of intracellular Bcl-2 was determined as described (32). Flow cytometric acquisition was performed on a FACSCalibur (BD Biosciences) and was analyzed using FlowJo (Tree Star) software.…”

More robust gut immune responses induced by combining intranasal and sublingual routes for prime-boost immunization

“…Antigen-specific germinal center B cells differentiate into Ig-secreting plasma cell and migrate to bone marrow, where they become the long-lasting plasma cells. 24 Memory B cells accumulate in the spleen, circulate among the body's chain of lymph nodes and maintain peripheral surveillance for the antigen. We quantified the long-lasting plasma cells in bone marrow (Fig.…”