A novel method for the diagnosis of Acquired Immune Deficiency Syndrome (A.I.D.S.) is disclosed, involving the use of immunocytoadherence (rosette inhibition) techniques. The method is based on the discovery that the lymphocytes of A.I.D.S. patients are unusually resistant to antithymocyte serum, and that the plasma of A.I.D.S. patients is capable of conferring this resistance to normal lymphocytes. Accordingly, the diagnostic method involves performing rosette inhibition tests on the patient's lymphocytes or on lymphocytes from a healthy donor after treatment with the patient's plasma. Any observable lessening of inhibition in comparison with a control is related to the presence of A.I.D.S.

An improved method for radio-labelling leucocytes in vitro with Tc-99m d,1-HMPAO (Technetium-99m-d,1-hexamethyl propyleneamine oxime) for use in scintigraphic imaging of inflammatory lesions enhances the labelling efficiency by incubating the leucocytes with Tc-99m d,1-HMPAO in the presence of an acid citrate dextrose solution and by depleting residual RBCs from the leucocytes prior to such incubation step. The RBC depletion is accomplished by means of a rocking step.

A method of inducing antitumor immunocytes which is simple in operation and suitable for inducing antitumor immunocytes having not only excellent cytotoxic activity against tumor cells but also high safety, which method comprises contacting leucocytes with an insoluble, antitumor immunocyte-inducing material capable of linking with T cells, said antitumor immunocyte-inducing material comprising an insoluble carrier and a ligand linked therewith. The induced antitumor immunocytes can be simply separated in substantially ligand-free form from the insoluble, antitumor immunocyte-inducing material. The obtained antitumor immunocytes have not only excellent cytotoxic activity against tumor cells but also high safety.

Disclosed is a method for separating leukocytes from platelets. Blood serum is added to a centrifuge tube. A suspension containing leukocytes and platelets is then added to form a layer on top of the blood serum, the layer having a density less than the density of the blood serum. The cells and the layers are centrifuged at a force and for a time sufficient to separate the leukocytes from the platelets. The resulting, isolated leukocytes are then recovered from the centrifuge tube. In some embodiments, a suspension of the leukocyte cells are pretreated by incubating with a stannous ion reducing agent, the suspension having a stannous ion concentration of from about 50 .mu.g to about 1000 .mu.g stannous ion per 10.sup.8 leukocyte cells. A suspension of the pretreated leukocyte cells is then incubated with a solution containing a technetium-99m (VII) salt, preferably sodium .sup.99m Tc-pertechnetate, to radiolabel the leukocyte cells.