Optimization of antigen presentation to T cell hybridomas by purified Ia molecules in planar membranes. Ia molecule polymorphism determines the antigenic fine specificity of the response to cytochrome c peptides.

Ia molecule (Ek,b beta:Ek alpha or Ak beta:Ak alpha)-containing planar membranes were constructed with cholesterol and a 9:1 molar ratio of the phospholipids dipalmitoyl phosphatidylcholine and dilinoleoyl phosphatidylcholine. This lipid composition was found to be optimal for the stimulation of T cell hybridomas of different specificities. Use of this system allowed the detection of weak responses not measurable when other artificial membranes were used. Activation of the cytochrome c, Ek,b beta:Ek alpha-reactive hybridoma 2B4.11 using such membranes resulted in responses comparable to those found using antigen-presenting cells (APC); that is, similar amounts of IL-2 were produced at the same concentrations of antigenic peptides. Presentation of moth and pigeon cytochrome c peptides by Ek beta:Ek alpha- or Eb beta:Ek alpha-reconstituted membranes resulted in 2B4.11 response patterns similar to those previously described using B10.A or B10.A(5R) APC. These data conclusively demonstrate that differential stimulation by moth and pigeon cytochrome c peptides depends solely on structural differences in the E beta:E alpha molecules used for antigen presentation.