Antisera to prostaglandins (PG) of the A, B, E and F groups were elicited by immunization with PG protein conjugates. Antibodies to PG of the A and B groups cross-react with each other, but discriminate these 2 groups of PG from those of the E and F groups. Antibodies to PG of the E groups, elicited with PG E-bovine serum albumin (PGE-BSA) conjugates in rabbits, cross-react with PG of the A and B groups. This cross-reaction is diminished by immunization of rats or mice with PGE-BSA, or by immunization of rabbits with PGE conjugated to to .gamma.-globulin or thyroblobulin. Antibodies to PGF have a marked group specificity and discriminate between this group of PG and PG of the A, B and E groups. All the antibodies produced do not discriminate between individual PG within the group.
