Suppression of chemotactic activity of human polymorphonuclears by monoclonal IgMs with and without biological activity

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Abstract
The influence of monoclonal IgMs on migration of human polymorphonuclears was studied at various temperatures by the use of 19 sera with monoclonal IgMs from patients with macroglobulinemia of Waldenstrom (MW) without obvious biological activity, 29 sera with monoclonal IgM cold agglutinins (18 with anti‐I and 11 with anti‐i IgMs) and 3 sera with monoclonal IgM rheumatoid factor (RF). Under‐agarose migration method and modified Boyden chamber method with double filters and 51Cr‐PMNs were used. In under‐agarose method, chemotactic differentials for controls, MW, anti‐I, and anti‐i groups were, respectively, 57 ± 8 mm, 39 ± 9 mm, 44 ± 14 mm, and 32 ± 16 mm at 37°C and 47 ± 18 mm, 22 ± 11 mm, 17 ± 9 mm, and 15 ± 12 mm at 24°C. All three sera with IgM RF inhibited chemotaxis. The differences between all groups and controls were significant at p < 0.01. Random migration was inhibited at 24°C (p < 0.01) but not at 37°C. Inhibitory concentrations of IgM in the sera tested were equal or less than 0.5 mg/ml. Thirteen sera were tested by the modified Boyden chamber method. At 37°C 8 of 13 sera and at 24°C 11 of 13 sera inhibited significantly chemotaxis at a concentration of IgM of 1 mg/ml. The lowest inhibitory concentration of IgM was 25 μg/ml. Eleven chromatographically pure IgMs were tested in the under‐agarose assay. At concentrations of 0.4‐3.7 mg/ml, eight IgMs inhibited chemotactic differential at 37°C and nine inhibited it at 24°C. At concentrations of 0.6‐2.0 mg/ml, all seven pure IgMs tested by the Boyden chamber method significantly inhibited chemotaxis at 24°C and 37°C. Some IgMs inhibited chemotaxis at concentrations as low as 25 μ/ml. Ten IgM CA were eluted from the red blood cells. Eluates inhibited strongly chemotaxis at 24°C and 37°C. Heat inactivation did not alter inhibitory activity of IgM, however pepsin digestion or reduction and alkylation of purified IgMs did abolish their inhibitory activity. Inhibition of chemotaxis was not related to the light chain type, the titre, or the thermoamplitude of cold agglutination. However, monoclonal IgMs with anti‐i cold agglutinin activity were stronger inhibitors than anti‐I. Since 75% of IgMs tested inhibited chemotaxis at 37°C, it is possible that monoclonal IgMs, especially those with anti‐i cold agglutinin activity, inhibit PMN migration in vivo.