The development of contact sensitivity to poison ivy urushiol in guinea pigs was prevented by intravenous injection of 3-n-pentadecylcatechol (I) coupled to autologous blood cells. Hartley, line-bred, guinea pigs were treated with pentadecylcatechol-"modified" blood cells or sham-treated blood cells 2 weeks prior to attempted topical sensitization with I. Skin testing of all guinea pigs with 3-, 1-, and 0.3-microgram doses of I applied in 5 microliter of acetone to abdominal skin sites was begun 2 weeks after attempted sensitization and repeated at 2- or 4-week intervals thereafter for 6 months or until study termination. Profound tolerance to I was observed at all skin testing intervals in the group receiving haptenated red cells and did not weaken with time. Contact sensitivity to I in control animals, however, waned with time; the study was terminated at 6 months because of the low sensitivity level of the control animals at that period. Complete or partial tolerance was induced in approximately 80% of the treated animals. The immune tolerance obtained by the single injection of pentadecylcatechol-associated red blood cells was of long duration and urushiol specific. This treatment also conferred tolerance to three unsaturated congeners of I. The allergenic potencies of the pentadecylcatechols declined with increasing saturation of the alkyl side chain. Binding studies using tritiated pentadecylcatechol showed that 81% of the activity incorporated into the red cell was membrane associated and that 19% was cell sap associated.
Animals Blood Cells