CD5+ B cells in autoimmune disease and lymphoid malignancy

Area of Science:

• Immunology
• Autoimmunity
• B cell biology

Background:

• CD5+ B cells represent a distinct lineage involved in natural immunity.
• These cells are linked to autoimmune diseases like rheumatoid arthritis and Sjögren's syndrome, and lymphoid malignancies.
• Their role in systemic lupus erythematosus (SLE) is debated, particularly regarding pathogenic autoantibody production.

Purpose of the Study:

• To investigate the role of CD5+ B cells in the production of pathogenic IgG autoantibodies in SLE.
• To explore the potential for CD5+ B cells to undergo phenotypic switching to CD5- cells.
• To examine the influence of genetic background on CD5+ B cell differentiation and disease outcome.

Main Methods:

• Studies utilizing SLE-prone NZB x NZW F1 mice and their H-2-congenic progeny.
• Analysis of autoantibody production (IgM and IgG anti-DNA).
• Assessment of CD5 expression on B cells and evaluation of B cell proliferation.

Main Results:

• Most IgM anti-DNA antibodies are produced by CD5+ B cells, while pathogenic IgG antibodies are mainly from CD5- B cells.
• A specific H-2-congenic NZB x NZW F1 mouse line failed to produce IgG anti-DNA antibodies but exhibited significant CD5+ B cell proliferation.
• Evidence suggests CD5+ B cells may switch phenotype to CD5- to produce pathogenic IgG autoantibodies under certain genetic conditions.

Conclusions:

• CD5+ B lineage cells may contribute to pathogenic IgG autoantibody production through phenotypic switching.
• Genetically determined signals can direct CD5+ B cells towards either autoimmune disease or lymphoid malignancy.
• Further research in congenic mouse models is crucial for understanding the autoimmunity-lymphoid malignancy correlation.