Immune precipitation from ¹²⁵I-labelled NA(1⁺,2⁺)-phenotyped neutrophils by neutrophil antisera and CD16 MoAbs. Lane 1, serum from the patient with the clinical pattern of primary AIN, but with chronic neutropenia. This serum reacted positively in the indirect GIFT and MAIGA with both NA(1⁺, 2⁻) and NA(1⁻, 2⁺)-phenotyped neutrophils. Lane 2, serum from a patient with secondary AIN with pan-FcγRIIIb antibodies as shown by the indirect GIFT. Lane 3, serum from a patient with primary AIN and NA1 antibodies, shown in the GIFT and the MAIGA. Lane 4, control serum containing isoantibodies with pan-FcγRIIIb specificity. Lane 5, MoAb CLB-gran11 (NA1-FcγRIIIb). Lane 6, MoAb CLB-FcRgran1 (pan-FcγRIIIb).