Influence of mouse genotype on passive systemic anaphylaxis by immune complexes

Area of Science:

• Immunology
• Genetics

Background:

• Passive systemic anaphylaxis (PSA) is an immune complex-mediated hypersensitivity reaction.
• The role of genetic background, specifically the H-2 haplotype, in modulating PSA severity is not fully understood.

Purpose of the Study:

• To investigate the influence of mouse major histocompatibility complex (MHC) H-2 haplotype on the development of passive systemic anaphylaxis.
• To elucidate the mechanisms underlying H-2-linked variations in PSA, focusing on complement system involvement and inflammatory mediators.

Main Methods:

• Induction of PSA using Brucella abortus endotoxin and rabbit anti-Brucella antisera in syngeneic and H-2 congenic mice.
• Assessment of PSA severity across different H-2 haplotypes (H-2b, H-2k, H-2d).
• Evaluation of the effects of complement inhibitors (suramin, flufenamic acid), a serotonin/histamine receptor blocker (cyproheptadine), and a thromboxane synthesis inhibitor (imidazol-alpha-ketoglutarate).

Main Results:

• Significant influence of H-2 haplotype on PSA sensitivity was observed, with H-2b being the most sensitive, followed by H-2k and H-2d.
• Variations in complement levels, potentially H-2-controlled, correlated with PSA sensitivity.
• Inhibition of PSA by cyproheptadine and imidazol-alpha-ketoglutarate indicated the involvement of platelet aggregation and inflammatory mediators.
• Differential effects of cyproheptadine and complement inhibitors suggested a role for early components of the classical complement pathway.

Conclusions:

• Mouse H-2 haplotype is a critical determinant of passive systemic anaphylaxis severity.
• Complement system activation, influenced by H-2 genotype, plays a significant role in PSA development.
• Platelet aggregation and mediators like histamine, serotonin, and thromboxane are important in this PSA model, with early classical pathway components being implicated.