What antibody is suspected if a serum tests positively with all cell types but negatively with cord cells?

The situation described in the question suggests that the serum has an antibody that reacts with all adult red blood cells types but does not react with cord cells. This pattern is characteristic of Anti-I antibodies, which are known to show strong reactivity with most adult red blood cells due to the presence of the I antigen, while they do not react with cord blood cells because those cells primarily express the i antigen. This differential reactivity provides a clear indication that Anti-I is present.

Individuals with Anti-I antibodies typically exhibit this pattern because as a person matures, red blood cells transition from expressing the i antigen to expressing the I antigen. Therefore, while the antibody attaches to the I antigen found on adult cells, it will not bind to the i antigen primarily found on cells from neonates, leading to a negative test with cord blood.

Other options, such as Anti-i, would not fit this pattern, as they would react with cord blood due to the presence of the i antigen on those cells. Anti-H typically would not have this specific reactivity either, as it generally interacts with the H antigen in the context of Bombay phenotype red blood cells. Lastly, Anti-p is not commonly associated with the pattern given in the question. Thus, the presence of Anti