Methyl groups as antigenic determinants in skin sensitisation

The methylating agents, methyl dodecane sulphonate, methyl hexadecane sulphonate and methyl hexadec-3-ene sulphonate are strong skin sensitisers, cross-reactive with one another, in guinea pig adjuvant tests. Differences in potency are observed among these 3 compounds, and the possible reasons for this are discussed. Isoeugenol fails to elicit a sensitisation response when challenged onto guinea pigs sensitised to methyl dodecane sulphonate, indicating that the mechanism of isoeugenol sensitisation is not based on methyl transfer. It is proposed that, in skin sensitisation involving small haptenic groups, antigenic specificity is directed not against the haptenic groups but against portions of the carrier protein whose configuration has been modified as a result of the carrier-hapten reaction. This concept is supported by published data on cross-reactivity patterns with enantiomeric pairs of alpha-methylene-gamma-butyrolactone derivatives.