Binding of purified human anti-Id antibodies (Ab2) to anti-gp43 MAbs. Plates coated with anti-gp43 MAbs 17c, 40.d7, 27a, 3e, and 8a were assayed for recognition by purified human anti-Id antibodies (Ab2). Positive reactions were only seen for MAbs 17c and 3e. MAb 6.C4 was used as a control. This plot is representative of three independent experiments. Error bars show standard deviations. O.D., optical density.