Faculty Bibliography

Allergic contract hypersensitivity (ACH)1 in young (3-5 mos.) and aged (16.18 mos.) BALB/c mice was evaluated by sensitizing the nape of the neck and subsequently challenging one ear with 1-chloro-2,4,6-trinitrobenzene (TNCB). Prior to sensitization, biopsy specimens of the contralateral unchallenged ears were obtained to determine the numbers of Ia+ Langerhans cells (LC) and mast cells (MC). Ear swelling responses, serum histamine levels, and histologic alterations of the challenged ears were evaluated in each age group at 0, 1.5, 4, 12 and 24 hrs. after challenge with TNCB. ACH was similar in young and aged mice during the first 12 hrs.; however, a significant difference in ear swelling was noted at 24 hrs. (38.0 .+-. 4.6 .times. 10-2 mm in young; 21.2 .+-. 2.0 in aged, p = 0.01.) There were no differences in MC number, degree of MC granulation, or serum histamine levels between young and aged mice at any time point. By 12 hrs., the inflammatory infiltrate in the ears of aged mice was slightly less intense and this difference became more marked at 24 hrs. At this time, the infiltrate consisted of neutrophils in young mice but continued to consist of mononuclear cells in the aged mice. Since the early ACH response in young and aged mice is similar, it is unlikely that decreased numbers of Ia+ LC in aged (449 .+-. 19 cells/mm2) as compared to young mice (720 .+-. 40) accounted for the decreased response at 24 hrs. We speculate that alterations in functional I cells in the age mice result in a diminished recruitment of neutrophils