In vivo studies on suppressor lymphocyte activity following administration of Escherichia coli O138 lipopolysaccharide.

Evaluation of Escherichia coli vaccines used in veterinary practice usually relates to antibody formation and neglects the essential characteristics of cell function leading to this end. This paper attempts to investigate the cellular responses to E coli O138 lipopolysaccharide (LPS) administered subcutaneously in a dose range of 1 microgram to 200 microgram. Rosette-forming cell responses in the draining lymph node varied from antigenic at 10 microgram to tolerogenic at 200 microgram. The tolerogenic dose also caused a marked mitogenic response as can be seen by a fourfold increase in total lymph node cells. Fractionation of normal or LPS-responding, or LPS-tolerised lymph node cells into B cell-rich and T cell-rich fractions was carried out and these were adoptively transferred simultaneously with an antigenic dose of sheep erythrocytes (SRBC) into syngeneic recipient mice. Suppressor activity of the anti-SRBC response was found after transfer of 1 X 10(6) normal B cell fractions, 1 X 10(6) tolerised B cell fractions and 1 X 10(6) tolerised T cell fractions. LPS-antigenically stimulated lymph node cell fractions had no suppressor effect but when given with Freund's complete adjuvant ensuing T cell-rich fractions produced immunosuppression in recipient mice. The significance of these findings is discussed in relation to polyclonal B cell activation, helper and suppressor T cells, and possible feedback mechanisms between interacting subpopulations of lymph node cells.