Figure 5.

Hindering auxiliary anchors modifies I-A^k binding and recognition. Register 1 HEL(48-61) P4, P6, P7, and P9 anchors were substituted with one, two, three, or four auxiliary anchors from each of the alternative registers (2, 3, or 4) and analyzed for binding. HEL(48-61) substitutions with register 2 and 3 auxiliary anchors also were analyzed for SDS/PAGE stability and half-life. Additionally, register 2- and 3-substituted HEL(48-61) peptides were incubated with I-A^k-bearing APC and offered to 3A9 T cell hybridomas. +++, maximal IL-2 response; ++, moderate IL-2 response; −, no IL-2 response. The maximal response corresponded to approximately 40,000–60,000 cpm at 0.1 μM, whereas moderate required 10- to 50-fold more peptide for a similar response. NB, nonbinding; ND, not determined because of poor binding.