What is the primary cause of Kell alloimmunization?

Kell alloimmunization primarily occurs due to prior transfusion. This condition develops when an individual who lacks Kell antigens on their red blood cells is exposed to RBCs from a donor who has these antigens. The immune system then recognizes the foreign Kell antigens as a threat and produces antibodies against them. This situation is particularly significant in blood transfusions, where the introduction of mismatched blood can lead to sensitization. Once sensitized, the individual remains at risk for future pregnancies or transfusions involving Kell-positive blood, potentially leading to hemolytic disease in the fetus or newborn.

In contrast, multiple pregnancies, high-risk sexual behaviors, and autoimmune disorders do not directly contribute to Kell alloimmunization in a similar manner. While multiple pregnancies could lead to increased exposure to antigens, they do not imply sensitization to Kell specifically. High-risk sexual behaviors and autoimmune disorders are also unrelated to the primary mechanism of sensitization that occurs with blood transfusions, where Kell antigens are introduced into a previously sensitized individual’s system.