Studies with radioiodinated cold agglutinins of ten patients

Abstract

The incorporation of I 131 into macromolecular cold agglutinins and purification by adsorption and elution from red cell stroma or whole red cells did not modify the serologic characteristics of the agglutinins. The radioiodination permits visualization of the relationship of antibody to red cells with varying concentration, temperature and pH. The equilibrium relationship between cold agglutinin and red cell is dependent on temperature but is also influenced by hydrogen ion concentration. Fixation of complement globulin to the red cell surface does not appear to bind cold agglutinin, which dissociates from the red cell leaving the complex EC′ 142. Some cold agglutinins produced hemolysis of red cells at body temperature even though agglutination did not occur above 31 °c. It is postulated that a transient combination of agglutinin and red cell above 31 °c. in the presence of complement was sufficient for some cold agglutinins to produce complement hemolysis. Complement depletion appeared to be the limiting factor in the chronic hemolytic process in three patients whose cold agglutinins produced hemolysis at 37 °c. Complement present in blood transfusions may precipitate exacerbations of hemolysis in such patients. Two patients whose cold agglutinins produced hemolysis only below 31 °c. had normal serum complement levels and were susceptible to acute hemolytic episodes when chilled. The red cells of normal subjects varied in their content of I factor. There appeared to be some correlation between the uptake at 25 °c. of the radioiodinated cold agglutinins and susceptibility of the cells to agglutination and hemolysis in vitro. Mechanical hemolysis produced at 5 °c. was independent of these factors and appeared to be a characteristic of the agglutinin. The cold agglutinins of eight of the patients in our series were more reactive with the I factor common to most human adult red cells than with the i factor. The cold agglutinins of two patients with hemolytic anemia apparently related to infections had greater affinity for the i cells of two adults and for cord cells. In both instances the cells of the patient were more reactive with anti-I cold agglutinins but were also shown to be susceptible to agglutination by their anti-i agglutinins. The I antigen was heat stable in stroma and appeared to be a polysaccharide. Heating human red cell stroma to 100 °c. increased the adsorption of radioiodinated cold agglutinin. Treatment of whole red cells with proteolytic enzymes also increased the adsorption of cold agglutinins and extended the thermal range of antigen-antibody reaction. Rabbit red cells appeared to have more I factor than the red cells of other mammals, including man, and had a more variable relationship with cold agglutinins in regard to the temperature of dissociation. Sheep cells appeared to have more i factor than the cells of other mammals tested. Treatment of I 131-tagged cold agglutinin with mercaptoethanol or d,l-penicillamine reduced the agglutination titer and the I 131 activity of cold agglutinins. Both activities were partially restored following removal of the mercaptanes by dialysis.