A modified agarose method for the detection of migration inhibitory factor (MIF) is described. This technique which employs human leukocytes as effector cells distinguished PPD-sensitive from nonsensitive individuals. Because of the improved sensitivity of this method, MIF activity could be detected in serially diluted supernatants. The antigen dependency of MIF was demonstrated by progressively diluting the supernatants (containing MIF) with antigen-free medium until MIF activity was undetectable; reconstitution of these supernatants with small amounts of PPD antigen restored 52ndash;85percnt; of the initial MIF activity. These studies suggest that human MIF is antigen dependent.
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