IgM Antibodies in Fish Mucus 1

Abstract

Discussion and Summary

As early as 1935, Nigrelli (4) observed that the mucus of certain fishes was toxic to parasites and suggested that this activity might be due to antibody or that the mucus itself might be toxic to parasites.

Our studies have indicated that normal gar mucus contains detectable antibody to several erythrocytes. Other work in this laboratory (Bradshaw, C. M., and Sigel, M. M., unpublished work) with mucus of normal snapper, Lutjaneus griseus, and normal bowfin, Amia calva, also demonstrated detectable antibody activity in surface mucus. After primary immunization of gar with SHE their surface mucus antibody levels increases considerably. Lower titers of hemagglutinin were recently reported by Fletcher and Grant in the mucus of plaice (5).

We have previously reported that normal gar serum contains cold agglutinins with maximum reactivity at 4°. Interestingly, the normal and immune mucus antibody titers were increased by downshifting the temperature from 35 to 20° but no further enhancement was noted at 4°.

The hemagglutinin in gar mucus has several properties of macroglobulin antibody. It is located in the excluded fraction from Sephadex G-200, its activity is removed by absorption with RAGIgM and it is totally susceptible to reduction. The absence of 7S immunoglobulin is consistent with our findings (Bradshaw, C. M. and Sigel, M. M., to be published) on the absence of 7S IgM in gar serum.

Fletcher and Grant (5) found that the antibody present in plaice serum and mucus was not retained by Sephadex G-200, and had similar carbohydrate and amino acid compositions. Although they did not determine the S value of the mucus antibody, the serum antibody had an S_20,w of 12.4. The provisional conclusion based on our investigation and on the findings of Fletcher and Grant (5) is that IgM of fish occurs as a macroglobulin secretory protein.