A prodromal phase of infection with the human immunodeficiency virus (hiv). laboratory criteria separating aids-related complex (arc) from aids include elevated or hyperactive b-cell humoral immune responses, compared to depressed or normal antibody reactivity in aids; follicular or mixed hyperplasia in arc lymph nodes, leading to lymphocyte degeneration and depletion more typical of aids; evolving succession of histopathological lesions such as localization of kaposi's sarcoma, signaling the transition to the full-blown aids.