Table 2.
Peptide binding to MHC DR2 and cytokine secretion by clones in response to different altered peptides
| Substitutions | Peptide binding DRβ1*1501 (IC50%, nM) | Ho.A226 Δ IFN-γ secretion, pg/ml | Ho.A226 Δ IL-10 secretion, pg/ml | ||||
|---|---|---|---|---|---|---|---|
| ⇑ | ⇑ | ⇓ | ⇑ | ||||
| Native | H | F | F | R | 2.0 | 816 | 201 |
| 93X | H | F | F | K | 4.1 | 0 | 0 |
| H | F | F | H | 6.3 | 0 | 0 | |
| H | F | F | L | 2.8 | 0 | 0 | |
| H | F | F | A | 3.5 | 0 | 0 | |
| H | F | F | D | 343 | 0 | 0 | |
| 91X | H | Y | F | R | 22 | 0 | 0 |
| H | H | F | R | 16 | 0 | 0 | |
| H | L | F | R | 5.5 | 0 | 0 | |
| H | A | F | R | 19 | 0 | 0 | |
| 90X/93K | K | F | F | K | 7.0 | 474 | 169 |
| A | F | F | K | 5.2 | 239 | 123 | |
| F | F | F | K | 2.0 | 407 | 157 | |
| D | F | F | K | 76 | 0 | 0 | |
| 91X/93K | H | Y | F | K | 2.1 | 685 | 175 |
| H | W | F | K | 20 | 254 | 115 | |
| H | H | F | K | 7.9 | 237 | 138 | |
| H | L | F | K | 7.6 | 471 | 121 | |
| H | A | F | K | 2.1 | 20 | 123 | |
| H | D | F | K | 423 | 0 | 0 | |
| 91Y/93X | H | Y | F | H | 13 | 0 | 0 |
| H | Y | F | L | 18 | 0 | 0 | |
| H | Y | F | A | 18 | 0 | 0 | |
| 92A* | H | F | A | R | 924 | ||
The binding of MBP peptides to purified DRβ1*1501 molecules and cytokine secretion values after 40 hr of stimulation with antigen (at 50 μM) are reported. The background secretion of IFN-γ, IL-10, or IL-4 by clone Ho.226 in the presence of APCs without antigen was undetectable. There was no measurable IL-4 production. A representative of three experiments is shown. ⇑, TCR contact; and ⇓, MHC contact.
*
Binding of the peptide HFAR, which has an alanine at residue 92, to MHC DR2 molecules.