The GA-R2 (also known as HIR2) monoclonal antibody specifically binds to CD235a and CD235b. CD235a is also known as Glycophorin A (GYPA, GPA, GLPA), Sialoglycoprotein alpha, MN sialoglycoprotein, or PAS-2. CD235b is otherwise known as Glycophorin B (GYPB, GPB, GLPB), Sialoglycoprotein delta, SS-active sialoglycoprotein, or PAS-3. CD235a and CD235b are type I transmembrane sialoglycoproteins that are expressed on human erythrocytes, erythroid precursor cells and certain leukemic cell types. CD235a carries blood group M and N antigens, whereas CD235b contains S, s, and U antigens. This antibody is useful for the identification and characterization of erythrocytes, certain myeloid leukemic cell types, and studies of erythroid cell development and infectious diseases with erythrocyte involvement. Glycophorins may play a role in preventing cell agglutination.