Rhesus factorAntigen factorAntibody factor is a protein found in blood that is represented by a + or – sign, which affects the compatibility of blood with other blood types.

The Rhesus (Rh) factor is a protein, or antigen, on the surface of red blood cells. Its presence is shown by a plus sign and its absence by a minus sign, as in A+ or A−, and it affects blood compatibility. Therefore, the correct choice is Rhesus factor.

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