Agglutination of Red Blood Cells by Natural Serum IgG and IgM Antibodies*
| RBC . | Serum . | Purified IgG . | IgM* . | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A . | B . | AB . | O . | A . | B . | AB . | O . | A . | B . | AB . | O . | |
| A | − | ++++ | − | ++++ | − | ++ | − | ++++ | − | +++ | − | ++++ |
| B | ++++ | − | − | ++++ | ++ | − | − | ++++ | +++ | − | − | ++++ |
| RBC . | Serum . | Purified IgG . | IgM* . | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A . | B . | AB . | O . | A . | B . | AB . | O . | A . | B . | AB . | O . | |
| A | − | ++++ | − | ++++ | − | ++ | − | ++++ | − | +++ | − | ++++ |
| B | ++++ | − | − | ++++ | ++ | − | − | ++++ | +++ | − | − | ++++ |
Red blood cells of individuals of blood groups A1 and B were incubated with serum diluted 1:10 in PBS, purified IgG from serum (1.0 mg/mL), and IgM (the IgG-depleted fraction of serum) (0.1 mg/mL) of individuals of blood groups A1, B, AB, and O for 45 minutes at 37°C. After addition of antihuman globulin, tubes were centrifuged, and agglutination assessed microscopically. Agglutination was graded from − to ++++ using a conventional grading system.