The ampicillin rash. Lymphocyte transformation by ampicillin polymer.

The ready polymerization of ampicillin in solution raises the possibility that high molecular weight forms of the drug may be responsible for some of the allergic reactions associated with its therapy. In vivo and in vitro reactivity to ampicillin polymer was investigated in patients with infectious mononucleosis as well as other individuals with and without a history of having received ampicillin. In vivo skin testing proved largely inconclusive, as did investigations of specific penicilloyl antibodies. However, peripheral blood leucocytes cultured in the presence of the polymer were found to incorporate radioactively labelled thymidine at a faster rate than control unstimulated cultures. This was accompanied by morphological transformation. The extent of lymphocyte stimulation encountered in vitro appeared to be independent of the donor's clinical state and previous history of therapy with penicillins. It is postulated that this ampicillin polymer-mediated lymphocyte stimulation may play a role in the development of the skin rash.