Immunostimulatory Properties of Carrageenans

Abstract

<p>The capacity of carrageenan to enhance the primary humoral immune response to foreign erythrocytes was assessed using the Jerne plaque assay. It was found that kappa-carrageenan had an adjuvant effect for both the IgM and IgG response of BALB/c mice to sheep red blood cells. This adjuvant effect was dependent on the dose of carrageenan administered, the genetic background of the experimental animals (BALB/c, C57BL/6, and BALB/c x C57BL/6 F₁ hybrid mice were used), the time of carrageenan injection (relative to antigen), and the type of carrageenan used (kappa-, iota-, and lambda-carrageenans were used).</p> <p>The direct addition of kappa-carrageenan to cultures of spleen cells also had an adjuvant effect for the anti-SRBC responses. This in vitro effect depended on the dose of carrageenan added, the genetic background of the spleen cell donors, and the type of carrageenan used.</p> <p>In order to assess the mode of action of carrageenan's (in vivo) immunostimulatory activity, the capacity of spleen cells from mice which had been injected with carrageenan to modulate an in vitro immune response was studied. It was found that carrageenan-treated cells released of soluble factor(s) which enhanced the in vitro anti-sheep red blood cell response of murine spleen cells. The amount of enhancement observed in vitro was directly correlated to the dose of carrageenan given in vivo suggesting that inducing the release of soluble enhancing factor(s) was the basis for carrageenan's adjuvant effect.</p> <p>Cell fractionation experiments revealed that the soluble enhancing factor(s) was produced by a non-adherent T-cell and that cell-cell interactions were involved in its production. The possibility that the soluble enhancing factor was interleukin 2 was discussed.</p>