Antibodies to morphine as indicators of chronic morphine intoxication and impaired immune reactivity.

Chronic morphine treatment of rats for 2 and 4 weeks led to an increase in morphine-binding cells in the spleen, despite the general reduction of mononuclear cell content in the spleen and thymus. Simultaneously, serum antibodies to morphine (AbM) in haemagglutination titres 1:20 and higher appeared in 50% and 80% of animals, respectively. Animals with high titres of AbM had much weaker immune response to a thymus-dependent antigen (sheep red blood cells).