ORAL PEPTIDOGLYCAN POLYSACCHARIDE STIMULATES SYSTEMIC IMMUNOCOMPETENCY IN GERM-FREE MICE

Germ-free and conventional mice were fed sterile peptidoglycan-polysac charide polymers to determine whether intestinal bacterial cell wall p roducts influence systemic immunity. Germ-free mice fed saline had sig nificantly less footpad swelling after challenge with sheep erythrocyt es than conventional mice. Feeding peptidoglycan polysaccharide polyme rs to germ-free mice restored their deficient cellular immune response to conventional levels. Feeding peptidoglycan-polysaccharide did not alter anti-erythrocyte antibody production in germ-free mice. Spontane ous in vitro proliferation of unfractionated splenocytes taken from ge rm-free mice fed peptidoglycan polysaccharide polymers was enhanced co mpared with proliferation of splenocytes from germ-free mice fed human serum albumin. In vitro conconavalin A stimulation of unfractionated splenocytes obtained from germ-free mice fed cell wall polymers result ed in a significant decrease in proliferation relative to that seen fo r germ-free mice fed human serum albumin. Respective proliferation res ults were abrogated when splenocytes were fractionated by removal of p lastic-adherent cells. These results suggest that luminal peptidoglyca n-polysaccharide polymers are important in the functional development of systemic cellular immunity, and that plastic-adherent splenocytes r egulate this response.