Variable Region Identical IgA and IgE to Cryptococcus neoformans Capsular Polysaccharide Manifest Specificity...

Area of Science:

• Immunology
• Molecular Biology
• Microbiology

Background:

• Antibody isotype switching, from IgM to IgG and IgA, alters antibody affinity and specificity.
• The impact of isotype switching on immunoglobulin E (IgE) specificity, compared to other isotypes, remains largely unexplored.

Purpose of the Study:

• To investigate whether immunoglobulin E (IgE) antibodies exhibit altered fine specificity compared to immunoglobulin A (IgA) antibodies when sharing identical variable (V) regions.
• To compare the functional properties and antigen-binding characteristics of V-region-identical IgE and IgA.

Main Methods:

• Comparison of fine specificity between V-region-identical IgE and IgA against Cryptococcus neoformans capsular polysaccharide.
• Utilizing nuclear magnetic resonance (NMR) spectroscopy with (15)N-labeled peptide mimetics to probe IgE and IgA paratopes.
• Assessing the opsonic activity and protective efficacy of IgE and IgA in a murine infection model.

Main Results:

• V-region-identical IgE and IgA antibodies displayed distinct specificities towards the Cryptococcus neoformans antigen.
• IgE exhibited a significantly faster peptide cleavage rate compared to V-region-identical IgG subclasses and IgA, indicating paratope alterations.
• Both IgE and IgA demonstrated opsonic capabilities and provided protection against C. neoformans infection in mice.

Conclusions:

• Variable (V) region expression within the context of the epsilon (ϵ) constant (C) region leads to greater specificity changes than observed with comparable IgG subclasses.
• These findings suggest that the constant (C) region, specifically alpha (α) and epsilon (ϵ), influences antibody function and contributes to the unique properties of IgE and IgA isotypes.