Characterization of cells of the B lineage in the human adult greater omentum

Abstract

Summary Peritoneal B cells and their omental precursors play an important role in the immune response of the peritoneal cavity and mucosal surfaces in mice. We have previously shown that peritoneal and mucosal B lineage cells are unlikely to be significantly linked in humans. However, the status of the omentum remains unknown. Here, using immunohistochemistry, we observed that sparse, quiescent B cells and occasional clusters of B cells were present in the omentum and that plasma cells, predominantly with cytoplasmic immunoglobulin G (IgG), were present. We analysed sequences of immunoglobulin genes amplified using reverse transcriptase–polymerase chain reaction (RT‐PCR) from the normal human greater omentum, and describe the characteristics of variable region genes used by IgG, IgA and IgM. We focused on the properties of IgVH4 and IgVH5 families to allow comparisons of like with like between different Ig isotypes and cells from different immune compartments. We observed that the IgM genes were derived from a mixed population with mutated and unmutated immunoglobulin sequences. All IgVH4 and IgVH5 genes used by IgA and IgG from omental cells showed evidence of somatic hypermutation but the load of mutations was not significantly different to that seen in either the systemic or the mucosal compartments. The trends observed, including the dominance of IgG plasma cells, the IgA1/IgA2 ratio being biased towards IgA1, JH1 usage, and a moderate level of somatic mutations, link omental B lineage cells with the systemic compartment. These observations reinforce previous studies highlighting the difference between human and murine B‐cell compartments and their relationship to the mucosal immune system.

Mouse and human intestinal immunity: same ballpark, different players; different rules, same score

“…16,46 B-1 B cells may originate in the fatty omentum in the peritoneum of mice, 47 but again there is no evidence that the adult human omentum contains B cells that might either be precursors of or substitutes for B-1 B cells in the murine peritoneum. 48 There is a link between the murine spleen and the mucosa in this context. It has been recently shown that in mice, B-1a B cells and mucosal IgA derive from lineage-negative precursors found in the fetal liver that reside in the spleen after birth.…”

Subepithelial dendritic B cells in orofacial granulomatosis

“…Use of the J1 segment of the heavy chain, for example, is seen in peripheral but not mucosal Bcell responses. 17 The VH1-46 segment is associated with the immune response to rotavirus, 18 and the VH5 family segments are associated with allergic disease. 19 We have used the criteria above to study B cells in the oral mucosa.…”

Transradial approach for noncoronary angiography and interventions

“…Additionally, the use of certain gene segments can reflect selection into a particular functional repertoire. Use of the J1 segment of the heavy chain, for example, is seen in peripheral but not mucosal B‐cell responses 17. The VH1‐46 segment is associated with the immune response to rotavirus,18 and the VH5 family segments are associated with allergic disease 19.…”