Preparation and neutralization characteristics of an anti‐CSF antibody

Nine of ten rabbits immunized with a partially purified L-cell CSF had demonstrable titers of anti-CSF activity. In vitro the antibody was markedly inhibitory to both post-endotoxin mouse sera and several mouse tissue extracts. CSF containing conditioned media prepared from a number of sources showed variable inhibition suggesting that murine CSF's may be characterized by marked antigenic differences. Human sources of CSF were also inhibited thus indicating a degree of cross-reactivity between murine and human factors. These studies may provide the initial steps toward definition of the role of CSF in vivo.