Organizing pneumonia as a side effect of ipilimumab treatment of melanoma.

Ipilimumab is one of the newly developed human monoclonal antibodies used in the treatment of metastatic melanoma. Its primary mechanism of action is a specific blockade of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), a T-cell receptor responsible for inhibition of lymphocyte activation. By blocking CTLA-4, ipilimumab enhances immune responses against tumor cells, but also exposes normal tissues to an increased risk of autoimmune phenomena as a potential side effect.