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Fc receptor for shark IgM.
L Haynes1, L Fuller, E C McKinney
1Department of Microbiology and Immunology, University of Miami School of Medicine.
Developmental and Comparative Immunology
|January 1, 1988
Summary
Researchers found Fc receptors for shark Immunoglobulin M (IgM) on shark leukocytes. These Fc receptors appeared early in evolution, with previous detection challenges linked to phagocytosis.
Area of Science:
- Immunology
- Evolutionary Biology
- Marine Biology
Background:
- Fc receptors mediate immune responses by binding to antibodies.
- The presence and function of Fc receptors in early vertebrate species like sharks are not well understood.
- Previous studies faced challenges in identifying Fc receptors for IgM in sharks.
Purpose of the Study:
- To demonstrate the existence of Fc receptors for shark IgM on shark leukocytes.
- To characterize the binding properties of these Fc receptors.
- To investigate the evolutionary origins of Fc receptors.
Main Methods:
- Leukocyte treatment with Cytochalasin D to inhibit phagocytosis.
- Erythrocyte-rosetting assays using shark anti-human antibody-coated human erythrocytes.
- Blocking assays with purified shark IgM, Fc5 mu fragments, and other proteins.
- Binding studies with radioiodinated IgM.
Main Results:
- Specific binding of shark IgM to shark leukocytes was demonstrated.
- Binding was confirmed to be saturable and reversible, indicative of receptor-ligand interactions.
- Fc receptors for IgM were found to be present on leukocytes, suggesting an early evolutionary appearance.
Conclusions:
- Fc receptors for IgM are present on shark leukocytes.
- The evolution of Fc receptors predates mammalian species.
- Phagocytosis-associated non-specific binding may have previously obscured Fc-mu receptor detection.