Detection of antibodies against various birds, particularly against exotic birds, can be facilitated using the sensitive immunofluorescent technique on avian fixed-intestine cryostat sections. Different fluorescent patterns corresponding to difTerent human anti-avian antibodies have been observed. Sixty of IOO human sera containing antibodies against one avian species, predominantly pigeon, reacted also with all other avian species intestines; the remaining forty were more specific and reacted with a few species only. Cross reactions with antigens in song bird intestines indicate the presence ofa broad spectrum of antibodies in patients with bird fancier's lung.Correspondence; Priv. Doz. Dr J.

A deletion of the immunoglobulin heavy chain (IgH) pseudo-gamma, gamma-2, gamma-4, epsilon, and alpha-2 constant region gene segments was found to segregate unchanged in three generations of a family. The IgG1 locus on the IgH allele carrying the deletion was expressed to the same extent as its normal counterpart. One individual who was heterozygous for the deletion had an IgG2 deficiency, whereas the four other heterozygous individuals had serum levels of IgG2 and IgG4 within the normal ranges. IgA2 levels were low or below the normal range in all heterozygous individuals. The data indicate that the expression of some Ig isotypes can be decreased by hemizygous deletions, possibly due to a lower probability for switching.