Observations on the ox cell haemolysins in human serum.

Ox haemolysin activity was estimated in 107 samples of serum, from patients with suspected glandular fever, and seventy samples from patients selected at random. The activity appeared to be in two groups: a low titre group (found in both glandular fever suspects' serum and normal serum) associated with a negative differential Paul–Bunnell test, and a high titre group (found only in the suspects' serum) associated with a positive differential Paul–Bunnell test. The `normal' (low titre) ox haemolysin was found to be removed by absorption with guinea-pig kidney suspension. A one tube ox haemolysin test for glandular fever is described, which appears to be specific and is easy to perform. Two separate antibodies appear to be responsible for the `glandular fever' ox red cell haemolysin activity, one reacting with determinants common to sheep and ox red cells, and one reacting with a determinant on ox, but not sheep, red cells.