The correct answer is Sheep erythrocytes. The most specific cells containing antigens that agglutinate with heterophile antibodies are sheep erythrocytes. Heterophile antibodies are weak antibodies than are produced due to responses to poorly defined antigens. The most common application is seen in mononuclear spot test, which is a form of heterophile antibody test in Epstein – Barr virus infection. Heterophile antibodies are significantly important in clinically detecting Epstein - Barr virus (EBV), which is the causative agent for infectious mononucleosis.
This test relies greatly on the agglutination of sheep Red blood cells (erythrocytes) with heterophile antibodies present in the patient’s serum. Although human erythrocytes and horse erythrocytes have antigen that can agglutinate with heterophile antibodies, sheep erythrocyte is the most specific cell containing antigen that can agglutinate with heterophile antibodies.