A unique immune response control locus mapping with the H-2D class I region

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• The immune response to polysaccharide antigens like Trinitrophenyl (TNP)-ficoll is complex and involves the major histocompatibility complex (MHC).
• Previous studies identified two complementing loci controlling this response within the murine MHC.

Purpose of the Study:

• To identify the molecular basis of the second locus of control for TNP-ficoll immune response, located between the S and D regions of the MHC.
• To characterize a novel molecule involved in this immune regulation.

Main Methods:

• Selection and use of a monoclonal antibody (48-21.7) that specifically blocks the in vitro primary response to TNP-ficoll.
• Protein precipitation, sequential immunoprecipitation with anti-MHC antibodies, and N-terminal amino acid sequencing were employed.

Main Results:

• Monoclonal antibody 48-21.7 precipitated a unique ~40 kDa protein.
• This protein showed no cross-reactivity with class I Db or Ia antigens.
• Amino acid sequencing revealed unique residues at invariant positions, suggesting a class I-like structure.

Conclusions:

• A unique class I-like molecule, encoded by genes between the S and D regions, is involved in the immune response to TNP-ficoll.
• This molecule represents a novel component of immune regulation for polysaccharide antigens.