Factor VIII related antigen positive macrophages and acquired immune deficiency syndrome (AIDS): a problem of antibody specificity.

A further histopathological complication of atypical mycobacterial infection in acquired immune deficiency syndrome (AIDS) is reported. Positive reactivity between mycobacterial antibodies within a polyclonal antiserum and mycobacteria within tissues resulted in false positivity with this reagent to factor VIII related antigen. This complication may be avoided either by prior testing of the antiserum, or by purification, or by the use of monoclonal antibodies. Histopathologists examining tissues from patients with AIDS and those with disseminated mycobacterial infections and using immunohistochemical techniques should be aware of this occurrence.