Protein A reactivity with mouse immunoglobulins. Structural relationship between some mouse and human immunoglobulins.

Abstract

Reactivity with staphyloccal protein A in normal mouse serum was localized to the electrophoretic γ region. After absorption of normal mouse serum with a protein A-containing Staphylococcus aureus strain, Cowan I, the γ globulin line could not be detected by immunoelectrophoresis. Similar absorption of a mixture of Fab and Fc fragments from mouse γG localized the activity in the Fc piece. To define this protein A reactivity further, M-components isolated from various mouse plasma cell tumor lines were studied. All six γ2a, γ2b and γ3 mouse myeloma globulins tested reacted with protein A, whereas four M-components of the γ1, γA and γM mouse immunoglobulin classes did not react. One human IgD and one IgE myeloma globulin were also tested. Neither reacted with protein A. Protein A reactivity thus seems to be a characteristic of mouse γ2a, γ2b, γ3 globulins as well as human IgG-1, -2 and -4 globulins.