Which antibody from the Kidd antigen system is associated with delayed hemolytic transfusion reactions?

Anti-Jka is the correct answer because it is one of the antibodies produced in response to the presence of Kidd antigens on red blood cells, specifically the Jka antigen. The Kidd blood group system includes the antigens Jka and Jkb, which can cause delayed hemolytic transfusion reactions due to their ability to induce the production of antibodies that are often not detected in pre-transfusion screening.

In many cases, patients who develop an immune response to these antigens, particularly Anti-Jka, do so after an initial transfusion where their own antibodies may not be detectable immediately, leading to a delay in hemolytic reaction symptoms. This can occur because the antibody levels can be low and may take time to build up after re-exposure to the antigen. In contrast, Anti-Fya (part of the Duffy system) and Anti-Lua (part of the Lutheran system) are associated with different antigen systems and do not typically lead to delayed hemolytic reactions in the same manner. Anti-Jkb can also cause reactions but is less commonly implicated compared to Anti-Jka.