Allelic differences affecting invariant chain dependency of MHC class II subunit assembly

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• The invariant chain (CD74) is crucial for the proper folding and trafficking of MHC class II molecules.
• Understanding the early assembly of MHC class II alpha and beta subunits with the invariant chain is vital for antigen presentation.
• Polymorphisms in MHC molecules can influence their interactions and assembly pathways.

Purpose of the Study:

• To investigate the role of the invariant chain in the assembly of polymorphic MHC class II alpha and beta subunits.
• To elucidate the structure and fate of MHC class II subunits in invariant chain-deficient cells with varying MHC haplotypes.
• To determine how allelic variations affect the association of MHC class II subunits with the invariant chain.

Main Methods:

• Analysis of MHC class II alpha and beta subunit assembly in invariant chain mutant mice.
• Characterization of subunit expression in splenocytes and activated B cells (LPS/IL-4 blasts).
• Conformational analysis of MHC class II heterodimers.

Main Results:

• MHC class II A alpha b and A beta b subunit assembly is highly dependent on invariant chain coexpression.
• Other allelic MHC class II products (A alpha kA beta k, E alpha kE beta k, A alpha dA beta d) can assemble efficiently without the invariant chain.
• The invariant chain's contribution to MHC class II subunit assembly varies significantly among different allelic variants.

Conclusions:

• Invariant chain's role in MHC class II assembly is haplotype-dependent.
• Polymorphic differences in MHC subunits influence their sequential association with the invariant chain.
• These findings highlight the complex interplay between MHC polymorphism and invariant chain in shaping immune responses.