CONTACT SENSITIVITY AND THE DNA RESPONSE IN MICE TO HIGH AND LOW-DOSES OF OXAZOLONE - LOW-DOSE UNRESPONSIVENESS FOLLOWING PAINTING AND FEEDING AND ITS PREVENTION BY PRETREATMENT WITH CYCLOPHOSPHAMIDE

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 36  (3) , 449-459
Abstract
Cyclophosphamide was used to assess the role of suppressor cells in the contact sensitivity reaction. A single painting with 300 .mu.g and 30 .mu.g oxazolone produced poor contact sensitivity reactions (ear swelling). Cyclophosphamide (200 mg/kg) 2 days before painting increased the response to the lower doses but had less effect on the response to 3 mg oxazolone. A single feed with 10 mg oxazolone caused strong contact sensitivity while lower doses (10-1000 .mu.g) caused poor responses. Cyclophosphamide increased the response to the lower doses but not to the highest dose of oxazolone. The poor response to painting and feeding lower doses of oxazolone may be due to a suppessor system which was sensitive to cyclophosphamide. When contact sensitivity was measured by arrival of radioactively labeled cells, cyclophosphamide had the greatest effect on cell arrival when high doses were fed. Ear swelling and cell arrival may measure separate aspects of the contact sensitivity response. The lower doses of oxazolone, which caused little contact sensitivity, reduced the response to a standard immunizing dose. This low dose unresponsiveness occurred after painting or feeding (Chase-Sulzberger phenomenon). It did not occur in mice treated with cyclophosphamide before the 1st exposure to oxazolone. The low dose unresponsiveness might be due to suppressor cells. The response to oxazolone was assessed by DNA synthesis in the regional lymph nodes. A small dose of oxazolone (30 .mu.g) caused a peak of DNA synthesis on day 4 while a high dose (3 mg) caused a peak on day 3. Pre-treatment with cyclophosphamide depressed the response to 30 .mu.g although it increased contact sensitivity. The secondary response was smaller than the primary on days 3, 4 and 5 after immunization but larger on day 2. The depression but not the increase was prevented by cyclophosphamide and was probably due to a suppressor system.

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