Richard S. Smith

An analysis of the immunological specificity of antiserum against human IgG F(ab)2

Inhibition of the interaction between 131I human Fab and a standard dilution of rabbit anti-human F(ab)2, as measured in the ammonium sulfate technique, has been utilized to study and quantitate differences in antigenic determinants associated with pooled IgG, isolated IgG from normal individuals, IgG myeloma proteins of the four known subclasses and IgA and IgM paraproteins. Isolated IgG from four normal individuals was as effective as pooled IgG as an inhibitor of the standard anti-F(ab)2-131I Fab system, indicating that the inhibition system may be used to quantitate small amounts of normal IgG, assuming a normal distribution of K and λ light chains. n nWhen K and λ type IgG paraproteins of the four known subclasses were assayed as inhibitors, the K type paraproteins were more effective than the λ type paraproteins. However, the two were additive when mixed in the proportion of 23 K and 13 λ. When K and λ type IgA and IgM paraproteins were used in the inhibition system, neither were as effective as IgG; however, the K type paraproteins were more effective as inhibitors than the λ type. The mixture of 23 K and 13 λ IgA and IgM paraproteins were not additive but instead were dilutional. The test offers a sensitive method for studying antigenic determinants of protein molecules, previously evaluated only by the precipitation reaction or hemagglutination.

Quantitation of IgG by the ammonium sulfate technique—II. The immunological specificity of antiserum against human IgG Fc☆

Abstract Studies were undertaken to test the efficiency and specificity of purified proteins to block the interaction between standard dilutions of 125I Fc and rabbit anti-human Fc in the ammonium sulfate system. Myeloma proteins of the IgG, IgA, IgD, IgE classes, Wadenstrom IgM and IgM from normal subjects were tested. The 125I Fc-anti-Fc system was found to be specific for γ heavy chains and failed to reveal cross reactivity with α, δ, ϵ, or μ heavy chains and K or λ light chains. Myeloma IgG exhibited some variation in reactive determinants within subclasses. Whereas three of the IgG subclas materials possessed a full complement of determinants homologous toIgG, a relative deficiency, or absence of a determinant (s), was noted in others. The attributes of the inhibition system to quantitatively measure IgG were further explored, utilizing sera of normal and hypogammaglobulinemic subjects as well as an IgG contaminated IgA preparation

Quantification of IgG by the ammonium sulfate technique—I. Interference of the primary interaction between 125I Fc and rabbit anti-human Fc

Abstract A sensitive, reproducible method to quantitate human IgG, utilizing 125I Fc, derived from either the papain sensitive (ps) or papain resistance (pr) conformational forms of IgG, as the test antigen in the ammonium sulfate technique is described. Since 125I Fc fragments so obtained are innately soluble in 45 per cent saturated ammonium sulfate, free antigen may be separated from bound antigen-antibody complexes. The test system takes advantage of the capacity of IgG containing materials to block the interaction between human 125I Fc and a standard rabbit anti-human Fc.