Soluble protein but not peptide administration diverts the immune response of a clonal CD4+ T cell population to the T helper 2 cell pathway.

BALB/c mice immunized with protein Ags such as OVA in adjuvant mount a Th1-type response. Inhibition of Th1 and development of Th2 cells can be induced by pretreating BALB/c mice with soluble OVA before priming. To investigate some aspects of this immune deviation in vivo, naive TCR transgenic T cells specific for the chicken OVA peptide 323-339 presented by I-A(d) molecules were adoptively transferred into normal BALB/c mice. The frequency and fate of the transferred T cells can be followed with an anti-clonotypic Ab. In response to priming with OVA in CFA, the transferred transgenic T cells expand and differentiate into Th1 cells producing IL-2 and IFN-gamma. If recipient mice are injected with soluble OVA before priming, the frequency of transgenic T cells is not affected, but their expansion in response to Ag priming is inhibited. Yet, the fewer transgenic T cells recovered are not anergic, they proliferate as control cells when restimulated in vitro by plate-bound anticlonotypic Ab or by Ag. Analysis of Th phenotype indicates that pretreatment with soluble OVA has suppressed Th1 cell differentiation in favor of the generation of Th2 cells producing IL-4 and IL-5. Pretreatment with soluble peptide 323-339 also inhibits Th1 cell development, but fails to induce Th2 cell differentiation. Thus, pretreatment with soluble protein Ag or with synthetic peptide inhibits Th1 cell development, but only protein, not peptide, administration can deviate the in vivo response of a clonal T cell population from the Th1 to the Th2 pathway.