Passive cutaneous anaphylaxis and vasoactive amine challenge in nude (nu/nu) mice. A comparison with nu/+, axenic and young normal animals.

Recent suggestions of a thymic origin or thymo-dependent differentiation of tissue mast cells prompted an investigation in the athymic nude (nu/nu) mouse. The outbred nu/nu examined were found to possess mast cells in at least comparable numbers to the phenotypically normal nu/+. These nu/nu were superior to nu/+ as recipient for mast cell-dependent, long latent period (IgE-type), passive cutaneous anaphylactic (PCA) reactions. A variety of studies performed, including competition with nu/+ serum, thymic restoration, quantitation of nu/+ homocytotropic antibody responses, comparison with axenic or young mice and time-course studies of skin sensitization suggested that the higher PCA titres in nu/nu skin were not entirely due to a lack of competitive inhibition of mast-cell sensitization. The nu/+ used in these studies were in fact poor IgE recipients, but were somewhat more sensitive than nu/nu to hypovolaemic shock induced by histamine and serotonin mixtures. Pretreatment with Bordetella pertussis greatly enhanced the sensitivity of nu/+, axenic, holoxenic and young normal mice to the vasoactive effects of histamine and serotonin, but was somewhat less effective in nu/nu and old mice.