Detection of tube agglutination 37 degrees C-only antibodies by solid-phase red cell adherence

There are no published data on the detection of tube agglutination (TA) 37 degrees C-only antibodies by solid-phase (SP) red cell adherence assays using anti-IgG-coated indicator red cells. Thirteen examples of TA 37 degrees C-only antibodies were tested by conventional SP methods. Four TA 37 degrees C-only antibodies failed to react by SP. Three were anti- Lea, considered clinically insignificant, and one was anti-E, an antibody of potential clinical significance. The remaining nine TA 37 degrees C-only antibodies reacted by SP, including three anti-c, two anti- D, two anti-E, one anti-N, and one anti-M. The anti-M reacted with indicator red cells that lacked the red cell antigen and failed to react with IgG-coated indicator red cells whose anti-IgG component had been neutralized, indicating the antibody contained an IgG component. Two anti-D and one anti-c continued to react in an SP test using neutralized anti-IgG antigen-positive indicator red cells, i.e., indicator binding independent of antiglobulin, suggesting an IgM nature to these antibodies. Therefore, many TA 37 degrees C-only antibodies can be detected by SP either through detection of an IgG component by the anti-IgG of the indicator red cells, or through IgM crosslinking of antigen-positive indicator red cells to antigen-positive SP reagent red cell membranes.