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Identification of two distinct CD5- B cell subsets from human tonsils with different responses to CD40 monoclonal
1Laboratory of Clinical Immunology, Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Insights
This study reveals that CD5- B cells, unlike CD5+ B cells, do not proliferate but do activate in response to stimuli. Some CD5- B cell subsets, however, show proliferation, suggesting a link to germinal center cells.
Area of Science:
- Immunology
- Cell Biology
Background:
- CD5+ B cells are well-characterized, but the function and subsets of CD5- B cells remain less understood.
- Understanding B cell subset responses is crucial for immune system research and therapeutic development.
Purpose of the Study:
- To investigate the in vitro response of distinct CD5- B cell subsets to various immune stimuli.
- To characterize the phenotype and activation markers of CD5- B cell subsets.
- To explore potential relationships between CD5- B cell subsets and other B cell populations like germinal center cells.
Main Methods:
- Isolation of CD5- B cell subsets from tonsillar B cells using Percoll density gradients.
- Stimulation of B cell subsets with CD40 monoclonal antibody (mAb), interleukin-4 (IL-4), and rabbit anti-human mu chain antibody (a-mu-Ab).
- Analysis of proliferation, IgM production, and expression of activation markers (CD69, CD25, CD71) via flow cytometry.
Main Results:
- Resting CD5- B cells failed to proliferate but expressed activation markers (CD69, CD25, CD71) upon stimulation.
- Purified germinal center cells responded robustly to CD40 mAb and IL-4.
- A subset of CD5- B cells from the 50% Percoll fraction exhibited proliferation and expressed a mantle zone B cell phenotype, suggesting a potential link to germinal center cells.
Conclusions:
- CD5- B cells exhibit distinct activation patterns compared to CD5+ B cells.
- The CD5- B cell population is heterogeneous, with a subset showing characteristics and responses similar to mantle zone B cells.
- Further research is warranted to elucidate the precise role and lineage relationships of CD5- B cell subsets in immune responses.
Abstract:
This study investigated the response of different CD5- B cell subsets to CD40 monoclonal antibody (mAb) in various combinations with interleukin (IL)-4 or rabbit anti-human mu chain antibody (a-mu-Ab). The different CD5- B cell subsets were isolated from tonsillar B cell suspensions depleted of CD5+ B cells and subsequently fractionated on Percoll density gradients. While resting CD5+ B cells proliferated and produced IgM molecules in response to a-mu-Ab, IL-4 and CD40 mAb as well as to Staphylococcus aureus Cowan strain I (SAC) and IL-2, resting CD5- B cells, which were co-purified in the same 60% Percoll fractions, consistently failed to respond. These cells were, however, activated by the stimuli employed, as demonstrated by their capacity to express the surface activation markers CD69, CD25 and CD71. Resting CD5+ B cells had the typical phenotype of mantle zone B cells (IgM+ IgD+ CD39+ CD38- CD10- CDw75dim), whereas resting CD5- B cells were CD38- CD39- CD10- CDw75 intermediate and expressed surface IgM but relatively little surface IgD and could not be classified as mantle zone or germinal center cells. The finding that purified germinal center cells (CD38+ CD10+ CD39- CDw75bright, IgG+) responded to CD40 mAb and IL-4 and also to SAC plus IL-2 further underlined the differences to resting CD5- B cells. However, some of the data collected suggest possible relationships between CD5- B cells and germinal center cells. The CD5- B cells isolated from the 50% Percoll fraction proliferated in response to a-mu-Ab, CD40 mAb and IL-4 as well as to SAC and IL-2. These cells had the same mantle zone B cell phenotype as the CD5+ B cells, but their capacity to respond to the stimuli in vitro was unrelated to a possible contamination with CD5+ B cells, as documented by the appropriate controls. Furthermore, upon exposure to SAC or phorbol esters, the large majority of CD5- B cells from the 50% Percoll fraction did not express surface CD5 and there was very little if any accumulation of CD5 mRNA. Finally, most of the cycling cells in the stimulated CD5- B cells did not express CD5. The CD5- B cells from the 50% Percoll fraction were comprised of a consistent proportion of cells that expressed surface activation markers.(ABSTRACT TRUNCATED AT 400 WORDS)
