Experimental exploration and model development is being pursued for analytical determination of the best configuration and composition of immuno-surfaces for capturing target antigen. The effects of antigen valency, size, and concentration on antigen capture is explored through modeling and analysis of experimental data obtained on a BIACORE 3000. The model of the antigen-immuno-surface interaction is based upon a two-compartment model that describes the mass transport-influenced binding of free analytes to the sensor surface. The lumped model considers the multivalent antigen as a whole with a single pair of association and dissociation rates that vary functionally with antigen valency to incorporate cooperative and steric hindrance effects. The lumped model is revised to incorporate antigen size effects; upon antigen binding, an exclusion area is created within the projection of the antigen on the surface. This effect becomes significant for bacteria target antigens on the scale of 0.1 to 10 microns in diameter, and is reflected in our model as a decrease in the effective surface density of free antibodies.