Observations on the 0 Antigen *

In a previous paper [l] one of us (E. G.) has reported variations in anti-0 sera and classified them into various types on the basis of their reactions with 0 cells of different types. The serum of a healthy “I negative” donor (C. G.) was tentatively classified as anti-0 type 4. This serum when investigated in Bristol with two “Bombay” type cells gave positive reactions with one and negative with the other. Both these o h type cells were glycerol stored and reconstituted. It was therefore decided to re-test the serum in one laboratory with a larger panel of freshly collected O h cells.