Journal of Experimental Medicine, Vol 145, 1029-1038, Copyright © 1977 by Rockefeller University Press
The role of fetal calf serum in the primary immune response in vitro
HG Opitz, U Opitz, H Lemke, G Hewlett, W Schreml and HD Flad
The mode of action of 2-mercaptoethanol (2-ME) on the primary immune
response in vitro was investigated. Fetal calf serum (FCS) was preincubated
with 2-ME and lyophilized to remove free 2-ME. This 2-ME- treated FCS was
able to substitute the function of adherent cells in the primary immune
response against sheep red blood cells (SRBC) in vitro; Fractionation of
2-tme-treated FCS on a Sephadex G-100 column showed that 2-ME acted on a
high molecular serum component which after activation, could substitute for
macrophages. In order to obtain a humoral immune response against SRBC in
vitro, spleen cells require selected FCS. These "good" sera could be
distinguished from "deficient" sera by their higher content of this
2-ME-activated factor. The height of the in vitro immune response to SRBC
was dependent on the amount of activated factor added to the culture
medium. FCS normally required in the culture medium could be completely
replaced by the factor- containing fraction without deleterious effect on
the culture medium. The factor should be added to the spleen cells during
the first 24 h of culture and remain there for 72 h in order to obtain an
optimal immune response. The factor could be partially absorbed by spleen
cells but not by SRBC. The relationship between macrophage, 2-ME, and FCS
in eliciting an in vitro primary immune response is discussed.