[Effects of codeine and morphine on the primary humoral immunity of the respiratory tract].

To investigate the effects of centrally acting antitussive drugs, codeine and morphine, on the humoral immunity in the respiratory tract, male guinea pigs were immunized either systemically (i.p.) or locally (intratracheally, i.t.) with sheep red blood cells (SRBC). The development of plaque-forming cells (PFC) was determined using the spleen (S-PFC) and tracheobronchial lymph node cells (T-PFC). (I) Number of S-PFC after i.p. immunization increased to the maximum on day 5. Peak number of S-PFC and T-PFC after i.t. immunization occurred on day 6. (II) i.p. immunization: The drugs were given i.p. for 5 days before or for 4 days after immunization. Morphine (5 mg/kg) given prior to the immunization decreased spleen cellularity. Pretreatments with codeine (15 mg/kg) and morphine (5 mg/kg) also markedly inhibited the number of S-PFC. These drugs given after the immunization hardly affected the number of S-PFC. (III) i.t. immunization: The drugs were given for 5 days before or after the immunization. Codeine (15 mg/kg) given prior to the immunization inhibited the number of S-PFC. Codeine (3, 15 mg/kg) and morphine (1, 5 mg/kg) given before and after the immunization markedly inhibited the number of T-PFC, dose-dependently. These results indicate that codeine and morphine affect the humoral immunity both locally in the respiratory tract and systemically, which cautions against an easygoing use in respiratory diseases.