Contact mmunotherapy s beleved to work by the nducton of type V hypersenstvty reacton. Ths cell-medated response s beleved to act aganst a complex of contact agent hapten, bound to proten of vral orgn wth the Langerhans cell as the ste of antgen formaton and presentaton.

n AA a decrease n CD4 to CD8 lymphocyte count from 4:1 to 1:1 occurs. A decrease n ntrabulbar CD6 lymphocytes and Langerhans cells s noted. Happle et al. proposed the concept of 'Antgenc competton,' where an allergc reacton generates suppressor T cells that nonspecfcally nhbts the autommune reacton aganst a har follcle consttuent. Expresson of class  and MHC molecules, whch are normally decreased n areas affected by AA, dsappear after topcal mmunotherapy treatment. Sgnfcant nonspecfc reducton n delayed type hypersenstvty reactons to unrelated antgens, occurng at remote stes, s reported. Contact allergens also tend to attract a new populaton of T cells n to the treated areas of the scalp, thus enhancng a clearance of putatve follcular antgen. A 'cytokne nhbtor' theory has been proposed, whch suggests a possble nterference of contact allergens wth the pre-exstng pronflammatory cytoknes and also ther contnued producton by follcular keratnocytes. The other events noted are a decrease n the rased nterferon g levels, ncrease n mRNA expresson of nterleukns 2, 8, 10, and tumor necross factor a n the lesonal skn. t s also consdered that nterleukn 10 s responsble for the effectveness of DPCP, by nhbtng T lymphocytes. n succesfully treated patents, ncreased levels of the tumor growth factor b was detected.

Mechansm of acton n treatment of warts s not clear but t trggers a nonspecfc cell-medated mmune response, trggerng vrus-nfected cell lyss and death. Alteratons n cytokne levels, nonspecfc nflammaton wth predomnance of CD8 T cells causng wart regresson and bndng of dphencyprone to wart protens nducng a specfc mmune reacton have been suggested. The latter s supported by the fact that warts at untreated stes may sometmes mprove or clear durng treatment wth abundant CD8 T cells beng recruted nto the leson.


The scalp or ventral aspect of left forearm s the usual senstzaton ste for AA and warts, respectvely. A cotton tpped applcator saturated wth 2% DPCP n acetone s appled, and patents are advsed to avod washng the area and protect t from sunlght for 48 hours. Applcatons of the contact allergen are repeated weekly wth ncreasng concentratons. The usual ntal concentraton of DPCP s 0.001-0.1% and ths s repeated weekly, to nduce a mld contact eczema, wth concentraton adjusted accordng to the response. An eczematous response (whch may occur after fve days or more) ndcates that senstzaton has taken place. A second applcaton may be made f necessary. Only 1-2% of the patents fal to senstze.

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