Antibody Repertoire Development in Fetal and Neonatal Piglets. VIII. Colonization Is Required for Newborn Piglets to Make Serum Antibodies to T-Dependent and Type 2 T-Independent Antigens

Abstract

Cesarean-derived piglets were reared for 5 wk under germfree conditions or monoassociated with a benign Escherichia coli (G58-1) or a enterohemorrhagic strain (933D) derived from O157:H7, and immunized i.p. with the T-dependent (TD) Ags fluorescein-labeled (FL) keyhole limpet hemocyanin or trinitrophenylated (TNP) keyhole limpet hemocyanin and the type 2 T-independent Ags TNP-Ficoll or FL-Ficoll. Only colonized piglets showed an increase in serum IgG, IgA, and IgM and had serum Abs to FL, TNP, and colonizing bacteria. While serum Abs to FL or TNP appeared following colonization alone, secondary responses were restricted to piglets immunized using TD carriers. While animals colonized with 933D had significantly higher total serum IgG and IgM levels and specific IgG Abs than those colonized with G58-1, no differences were seen in serum IgA levels, B cell diversification in the ileal Peyer’s patches, and specific activity (ELISA activity per micrograms of Ig) of pre-boost serum IgG and IgM anti-TNP and anti-FL Abs. Serum IgA Abs to TNP, FL, or bacteria were not detected. Ag-driven responses, as measured by an increase in specific Ab activity, were only observed in secondary responses to TD Ags and to colonizing, pathogenic E. coli. We propose that germline-encoded, isotype-switched B cells in newborn piglets differentiate to Ab-secreting cells 1) after stimulation by bacteria-activated APCs or 2) through direct stimulation by bacterial products. We further propose that Ag-driven systemic responses require both bacterial colonization and TD Ags translocated to the peritoneum.

The postnatal development of the mucosal immune system and mucosal tolerance in domestic animals

“…In conventional piglets or in piglets specifically colonised with flora, V-segment usage in the intestinal mucosa expands, indicating that microbial colonisation drives expansion of repertoire, as well as compartments. Consistent with this, germ-free pigs mount poor specific systemic antibody responses [13], unless colonised with commensal flora. Even mono-association with a single commensal appears to be able to promote both a specific and a polyclonal expansion of IgM, IgG and IgA secreting lymphocytes in the mesenteric lymph nodes, spleen and Peyer's patches [16].…”

Antibody Repertoire Development in Fetal and Neonatal Piglets. XX. B Cell Lymphogenesis Is Absent in the Ileal Peyer’s Patches, Their Repertoire Development Is Antigen Dependent, and They Are Not Required for B Cell Maintenance

“…In piglets maintained germ-free (GF), the length of the IPP actually increases, suggesting that without environmental stimuli, their possible status as a primary B cell organ may continue (12). In conventional or colonized piglets IgA production becomes dominant (21). The observation that hindgut lymphoid tissues change their function during postnatal development has also been reported in rabbits (22).…”

Antibody Repertoire Development in Fetal and Neonatal Piglets: XIX. Undiversified B Cells with Hydrophobic HCDR3s Preferentially Proliferate in the Porcine Reproductive and Respiratory Syndrome

“…All studies were approved by the Animal Care and Use Committee of the NADC (Ames, IA). Most animals remained germfree whereas others were colonized with benign Escherichia coli as described previously (52), although we previously showed that E. coli colonization did not affect our results (12). Groups of three to five piglets from the same litter were used and were treated one of three ways: 1) inoculated intranasally with 10 4 TCID 50 PRRSV; 2) inoculated intranasally with 10 4 TCID 50 SIV; or 3) given a sham inoculum.…”

“…The BAL cell pellet was suspended in TRIzol and frozen at Ϫ20°C. Blood collected in anticoagulation tubes was processed as previously described for the recovery of PBMC and plasma (12,52,53). The plasma was used for Ig determinations and was cultured for virus as described previously (54).…”