Final answer:
A person with type A blood will have anti-B antibodies in their serum, which are capable of causing agglutination if RBCs with B antigens are introduced into the bloodstream. These antibodies are naturally formed in early life due to environmental exposure.
Step-by-step explanation:
If a patient has type A blood, his/her serum will contain anti-B antibodies. This is because people with type A blood have A antigens on the surface of their red blood cells (RBCs) and produce antibodies against the B antigen, which are not present on their own RBCs. These antibodies are IgM isohemagglutinins and have the potential to cause agglutination if RBCs with B antigens are introduced into the bloodstream.
For example, if type A blood is exposed to type B or AB blood, the anti-B antibodies in the type A blood will bind to the B antigens on the foreign RBCs, leading to clumping (agglutination) and potentially causing severe reactions. These antibodies are formed early in life in response to environmental exposure to ubiquitous antigens that are similar to blood group antigens. This process of antibody formation occurs without the need for prior exposure to blood transfusion or incompatible blood types.