The avian B‐cell receptor complex: distinct roles of Igα and Igβ in B‐cell development

Abstract

The bursa of Fabricius has evolved in birds as a gut-associated site of B-cell lymphopoiesis that is segregated from the development of other hematopoietic lineages. Despite differences in the developmental progression of chicken as compared to murine B-cell lymphopoiesis, cell-surface immunoglobulin (sIg) expression has been conserved in birds as an essential checkpoint in B-cell development. B-cell precursors that express an sIg complex that includes the evolutionarily conserved Igalpha/beta heterodimer colonize lymphoid follicles in the bursa, whereas B-cell precursors that fail to express sIg due to non-productive V(D)J recombination are eliminated. Productive retroviral gene transfer has allowed us to introduce chimeric receptor constructs into developing B-cell precursors in vivo. Chimeric proteins comprising the extracellular and transmembrane regions of murine CD8alpha fused to the cytoplasmic domain of chicken Igalpha efficiently supported B-cell development in precursors that lacked endogenous sIg expression. By contrast, expression of an equivalent chimeric receptor containing the cytoplasmic domain of Igbeta actively inhibited B-cell development. Consequently, the cytoplasmic domains of Igalpha and Igbeta play functionally distinct roles in chicken B-cell development.

Cells diversify transmembrane signaling through the controlled chaos of protein disorder

“…Another MIRR, FcεRI, generates the activation signal using 2 ITAMs of the FcεRIβ and FcRγ chains. Most of experimental data in the literature reported to date strongly support the distinct rather than redundant functions for the ITAM signaling modules including those located on the different signaling chains 39,[44][45][46][47][48][49][50][51][52][53][54][55] and those located on the same signaling module (e.g., 3 different ITAMs on TCR ζ chain). 56 Within the SCHOOL model, 10,11,42,43 cytoplasmic homooligomerization controls the ITAM signaling through the different patterns of MIRR signaling subunit homooligomerization 11,43 that produce distinct activation signals provided by different ITAMs.…”

Effects of Exogenous Proteins Injection into the Bursa of Fabricius on Humoral Immunity in Neonatal Chickens

“…Previous reports have shown that intra-follicular redistribution of bursal B cells represents a second checkpoint during chicken B cell development (Pike et al, 2004). Ag-dependent positive selection results in the migration of Ag-specific B cells from the medulla to the cortex (Pike and Ratcliffe, 2002), and surface IgG ＋ cells are localized to the medulla of bursal follicles after hatching (Ekino et al, 1995).…”

“…The bursa of Fabricius is the primary site for B cell development in chickens (Ratcliffe and Paramithiotis, 1990;Sayegh and Ratcliffe, 2000;Pike and Ratcliffe, 2002;Pike et al, 2004). During bursal development, colonization of lymphoid precursors occurs between 7.5 embryonic development day (E7.…”

“…In addition, the complete Ag recognition unit is not present in the pro-or pre-B cell receptor (BCR) (Fuentes-Panana et al, 2004). Bursal B cells expressing SIg ＋ represent a second checkpoint during chick-en B-cell development (Pike et al, 2004). Ag-dependent positive selection results in the development and movement of B cells from the medulla to the cortex .…”

B cell receptor accessory molecules in the channel catfish, Ictalurus punctatus

“…While several studies have confirmed that the chicken BCR complex also contains a homolog to CD79b, which is structurally and functionally equivalent to the mammalian BCR complex [29][30][31][32][33], little is known about B cell signaling and B cell accessory molecules in ectothermic vertebrates. However it is well established that these animals produce antibodies and have mIg on the surface of their B cells, also data-mining has identified CD79a and CD79b sequences in the pufferfish, Takifugu rubripes and rainbow trout, Oncorhynchus mykiss [34].…”