Antibodies to the Ch/Rg antigens are some of the most common "HTLA" antibodies seen in the blood bank. These antigens are destroyed by enzymes, but if enzymes are not available, there is another method that can assist you in identifying these antibodies—neutralization.
Normal plasma is likely to contain C4, which carries Ch/Rg antigens. Mixing the patient's plasma with an equal amount of a pool of normal plasma should cause the anti-Ch or anti-Rg circulating in the patient to bind to the antigens in the normal pooled plasma. Because they are already bound to their corresponding antigen in the pooled plasma, they should not bind to the antigens present on the previously reactive panel cells, producing negative results.
It is important to run a control when using this method to ensure that the negative reactions obtained with the pooled plasma are not due to dilution causing the levels of circulating antibodies to dip to undetectable levels. To accomplish this, run the previously reactive panel cells with patient plasma mixed with an equal amount of an inert control, such as bovine albumin, in parallel. If the control is reactive, the results of the neutralization with pooled plasma are valid and the anti-Ch/anti-Rg is confirmed.
