What is the likely cause of serum incompatibility with O cells when a patient's RBCs show a negative reaction to anti-H lectin?

What is the likely cause of serum incompatibility with O cells when a patient's RBCs show a negative reaction to anti-H lectin?

• A. The patient may be a subgroup of A
• B. The patient may have an immunodeficiency
• C. The patient may be a Bombay
• D. The patient may have developed alloantibodies

Answer: (C)

In the context of the question, the situation described involves a patient whose red blood cells (RBCs) show a negative reaction to anti-H lectin. Anti-H lectin reacts with the H antigen, which is present on the RBCs of most individuals. However, the Bombay phenotype is characterized by the absence of the H antigen, making these individuals unable to express A or B antigens and, consequently, they can react negatively to anti-H lectin. The scenario presented indicates serum incompatibility with O cells, which typically express high levels of H antigen. If the patient's RBCs are compatible with O cells in terms of ABO group but show a negative reaction to anti-H, it suggests that the patient does not produce the necessary antigens. In this case, being of the Bombay phenotype would mean that the patient has received serum from a typical O type individual, resulting in an incompatibility due to the absence of H antigen on their own RBCs. This phenomenon is unique to individuals with the Bombay phenotype, making it the likely cause for the incompatibility observed. Therefore, identifying the patient as having the Bombay phenotype explains the impossibility of proper interaction with O blood, which relies on the presence of H antigen for compatibility.

In the context of the question, the situation described involves a patient whose red blood cells (RBCs) show a negative reaction to anti-H lectin. Anti-H lectin reacts with the H antigen, which is present on the RBCs of most individuals. However, the Bombay phenotype is characterized by the absence of the H antigen, making these individuals unable to express A or B antigens and, consequently, they can react negatively to anti-H lectin.

The scenario presented indicates serum incompatibility with O cells, which typically express high levels of H antigen. If the patient's RBCs are compatible with O cells in terms of ABO group but show a negative reaction to anti-H, it suggests that the patient does not produce the necessary antigens. In this case, being of the Bombay phenotype would mean that the patient has received serum from a typical O type individual, resulting in an incompatibility due to the absence of H antigen on their own RBCs.

This phenomenon is unique to individuals with the Bombay phenotype, making it the likely cause for the incompatibility observed. Therefore, identifying the patient as having the Bombay phenotype explains the impossibility of proper interaction with O blood, which relies on the presence of H antigen for compatibility.