Histological study of mammae in oestrogenized rats after mammary isoimmunization.

Inoculation of 0·1 ml of an emulsion of a saline suspension of allogeneic lactating mammae and Freund's complete adjuvant into oestrone-primed female Wistar rats evoked in their mammary glands a progressively increasing focal mononuclear leucocytic infiltrate that was found in 25·0% of the animals 28 days after inoculation. Comparable changes were not seen during the experimental period in rats administered oestrone alone, or in those inoculated with other combinations of saline, lactating mammary or liver homogenates and Freund's complete or incomplete adjuvants. The mononuclear inflammatory lesions were substantially unaffected by the site of the intradermal inoculations, or by the addition of pertussis vaccine to the inocula, but were suppressed by antilymphocyte serum. It is suggested that some examples of human periductal mastitis may have an autoallergic basis.