ROLE OF MATERNAL ANTIBODY IN THE INDUCTION OF VIRUS-SPECIFIC AND BYSTANDER IGA RESPONSES IN PEYERS-PATCHES OF SUCKLING MICE

Reciprocal crossings of C.B17 scid/scid and congenic BALB/c (+/+) mice generate genetically identical, immunocompetent F-1 scid/+ mice that develop in either the absence or influence of passively transferred ma ternal immunity. By exchanging F-1 scidl+ litters at birth among scid/ scid, non-immune or reovirus immune BALB/c mothers we examined the rel ative ability of placental or colostral/milk transfer of Virus specifi c maternal antibodies to interfere with reovirus immunization of the n eonatal gut associated lymphoid tissues (GALT). Our data demonstrate t hat the Peyer's patches (PP) in 10-day-old mice are competent to suppo rt thymus dependent responses to acute reovirus stimulation that inclu de the rapid (within 3 days) development of specific IgA plasma cells and the subsequent initiation of PP germinal center reactions. These n eonatal mucosal immune responses occur independently of coincident spe cific maternal immune responses as evidenced by the identity of the re ovirus specific responses engendered in F-1 scid/+ pups of scid/scid v ersus +/+ mothers, However, transfer of pre-existing reovirus specific maternal antibody in milk via nursing on a reovirus immune (foster) m other completely abrogated reovirus specific neonatal IgA responses; w hile placental transfer of specific maternal antibody alone did not in terfere with the immunization of the neonatal GALT with enteric reovir us. Reovirus challenge of 10-day-old mice was associated with a substa ntial bystander IgA response. Possible mechanisms responsible for the induction of the observed bystander IgA responses are discussed.