Joining-chain (J-chain) negative mice are B cell memory deficient

Area of Science:

• Immunology
• Molecular Biology

Background:

• The joining-chain (J-chain) is crucial for the assembly of multimeric immunoglobulin (Ig) molecules, particularly IgM and IgA.
• Its role in T-dependent B cell responses and memory formation requires further elucidation.

Purpose of the Study:

• To investigate the systemic immune response in J-chain-deficient (J(-/-)) mice against a specific hapten (NP).
• To determine the impact of J-chain deficiency on primary and secondary humoral immune responses and B cell memory.

Main Methods:

• Analysis of systemic immune responses in J(-/-) mice and wild-type (WT) controls against the hapten 4-hydroxy-3-nitrophenyl (NP).
• Assessment of serum IgG levels, B cell numbers, immunoglobulin repertoire switching (lambda to kappa), and somatic mutations in the V(H) 186.2 gene.
• Adoptive transfer experiments using T cells from J(-/-) mice.

Main Results:

• Primary IgG responses to NP were comparable between J(-/-) and WT mice.
• Secondary immune responses were significantly compromised in J(-/-) mice, evidenced by reduced serum IgG and fewer responding B cells.
• Diminished lambda to kappa repertoire switching and reduced somatic mutations in the V(H) 186.2 gene were observed during secondary responses.
• Adoptive transfer confirmed that T cells from J(-/-) mice transferred the compromised secondary immune response.

Conclusions:

• J-chain deficiency results in a selective defect in T helper cell function during B cell immune responses.
• This defect leads to impaired B cell memory formation in the absence of functional J-chain.
• The study highlights a novel role for J-chain in regulating T cell-dependent B cell memory.