Subpopulations of B cells distinguished by cell surface expression of Ia antigens. Correlation of Ia and idiotype during activation by cloned Ia-restricted T cells.

Abstract

The induction of antibody responses to phosphorylcholine (PC) by cloned [mouse] T helper (Th) cell lines was investigated in vitro. The cloned Th cells were antigen specific, in this case for ovalbumin (OVA), self-Ia recognizing and induced antibody secretion only if the hapten, PC, was physically linked to the carrier (OVA) molecule. The plaque-forming cell (PFC) response generated in the presence of cloned Th cells was idiotypically diverse with 5-40% of the secreting B cells bearing the TEPC-15 (T15) idiotype. The interaction of the cloned Th cells and unprimed B cells required recognition of B cell surface Ia glycoproteins for all B cells activated to secrete anti-PC antibody, whether they be T15-bearing or not. Effective interaction between a cloned Th cell and a B cell was determined by the quantity of B cell surface Ia glycoproteins. Quantitative differences in B cell surface Ia antigens were directly related to B cell activation by the cloned Th cell. The high Ia density B cells were most easily activated by cloned Th cells; these appeared to be mainly non-T15-bearing. The failure of cloned Th cells to effectively activate T15-bearing B cells in vitro may be due to the lower relative Ia density of these B cells and therefore to their inability to interact effectively with cloned Ia-recognizing Th cells. Monoclonal T cells may distinguish between T15-bearing and non-T15-bearing B cells based on their Ia density.