Purpose of review: A number of studies over recent years have shown the relevance of nonimmediate immunological reactions to drugs and emphasized the need for these reactions to be studied in greater depth, including both in-vivo and in-vitro tests and provocation studies.
Recent findings: Several clinical entities are involved, ranging from mild to severe reactions. Nonimmediate reactions have a special tropism for the skin, although other organspecific or systemic reactions may also occur. In the affected organ, the drug acts as a hapten or protohapten, originating an immunological stimulus that is followed by recruitment of T lymphocytes and other types of cells, depending on the reaction. This involves a trafficking phenomenon in which these cells use different receptors that interplay with their corresponding ligands in the tissue. In addition, a number of activation and cytotoxic markers are also expressed, which are related with disease severity.
Summary: Current studies provide overwhelming evidence of the interaction between the organ involved, very often the skin, and immunocompetent cells. This is of relevance for diagnostic and therapeutic approaches.