What primary factor contributes to platelet refractoriness in patients?

Platelet refractoriness is a condition where a patient fails to achieve a satisfactory increase in platelet count following platelet transfusion. The primary factor contributing to this condition is the presence of antibodies against HLA (human leukocyte antigen) Class I molecules.

When a patient has been sensitized to HLA antigens, either through previous transfusions, pregnancies, or organ transplants, they may develop antibodies against these antigens. In subsequent platelet transfusions, the transfused platelets may express the same HLA antigens against which the patient has developed antibodies. Consequently, these antibodies can bind to the platelets, leading to their destruction and preventing an adequate increase in platelet count.

The other types of antibodies mentioned, such as anti-HPA (human platelet antigen) and anti-HNA (human neutrophil antigen) antibodies, can also cause refractoriness but are generally more specific and less common in clinical scenarios. HPA-related refractoriness is often associated with a specific antigen-matching issue, while HNA antibodies predominantly affect granulocyte transfusions rather than platelets. Therefore, while these antibodies can contribute to platelet refractoriness, HLA Class I antibodies are the most significant and common primary factor.