Cimetidine and Common Variable Hypogammaglobulinemia

To the Editor: The development of effective therapeutic strategies based on in vitro pharmacologic data is fraught with difficulty, and this may be especially true in the case of putative “immunomodulators” such as cimetidine. In their report in the January 24 issue of the Journal,¹ White and Ballow review a large body of information establishing that histamine can enhance the activity of suppressor T cells in vitro. Many of these effects can be reversed by cimetidine, an antagonist of H₂ receptors. But attempts to use H₂ antagonists to influence immunologic responses in vivo have produced conflicting results.