In Ouchterlny immunodiffusion, what does a spur at the intersection of two lines indicate about the relationship of the two antigens?

In Ouchterlny immunodiffusion, what does a spur at the intersection of two lines indicate about the relationship of the two antigens?

• A. Antigens 1 and 2 are identical.
• B. Antigen 2 is simpler than antigen 1.
• C. Antigen 2 is more complex than antigen 1.
• D. The two antigens are unrelated.

Answer: (C)

In this test, spurs in the Ouchterlny immunodiffusion pattern tell you that the two antigens share some epitopes but differ by additional determinants in one of them. The spur extends toward the well with the antigen that has that extra determinant, because antibodies react with both the shared epitopes and the unique determinant. So a spur at the intersection indicates partial identity with one antigen being more complex than the other. In this case, antigen 2 has the extra determinants and is more complex than antigen 1.

In this test, spurs in the Ouchterlny immunodiffusion pattern tell you that the two antigens share some epitopes but differ by additional determinants in one of them. The spur extends toward the well with the antigen that has that extra determinant, because antibodies react with both the shared epitopes and the unique determinant. So a spur at the intersection indicates partial identity with one antigen being more complex than the other. In this case, antigen 2 has the extra determinants and is more complex than antigen 1.