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1. The removal of the ß2A-globulins from three sera from treated ragweed-sensitive individuals by immune absorption was associated with the loss of all detectable skin-sensitizing antibody activity as demonstrated by Prausnitz-Küstner testing. 2. Gel filtration studies, with sephadex G-200, indicated that the fractions containing only macroglobulins were devoid of all detectable skin-sensitizing antibody activity. 3. The immune absorption of the γ-globulins from a serum fraction containing ß2A-globulins, γ-globulins, and a trace of ß2M-globulins had no detectable influence on the skin-sensitizing antibody activity. 4. The removal of a portion of the albumin from the allergic sera by immune absorption, with retention of the skin-sensitizing activity, indicated that the loss of skin-sensitizing antibody was not due to non-specific absorption on an antigen-antibody precipitate. 5. No inhibition of the Prausnitz-Küstner reaction was observed when sheep serum, normal human serum, or normal human γ-globulins were tested in concentrations described. 6. We conclude that the skin-sensitizing antibody activities in the three sera from treated ragweed-sensitive individuals studied were associated with the ß2A-globulins.

We have shown that platelets are capable of phagocytosing liposomes rather than simply sequestering par- membrane marker. Uptake was inhibited by the addition of EDTA, cytochalasin B, or 2,4-dinitrophenol and iodoacetate to the medium. Results from the serotonin release assay, microaggregation assay, fluorescein diacetate membrane integrity assay, and electron microscopy indicate that neither the conditions for loading nor phagocytosis ofliposomes significantly alter platelet function or morphology.

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