Which among the following body secretions does NOT contain ABO antigens?
**Core Concept**
The presence of ABO antigens in body secretions is determined by the **ABO blood group system** and the **secretor status** of an individual. Most individuals are secretors, meaning they express ABO antigens in their bodily fluids.
**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the general principle: ABO antigens are typically found in secretions such as saliva, semen, and vaginal fluids in individuals who are secretors. However, one type of secretion does not contain these antigens due to its composition or function.
**Why Each Wrong Option is Incorrect**
**Option A:** Typically, saliva contains ABO antigens in secretors.
**Option B:** Semen is another secretion that usually contains ABO antigens.
**Option C:** Vaginal fluids can also have ABO antigens in secretors.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that not all bodily secretions contain ABO antigens, and this can be crucial in forensic medicine.
**Correct Answer:** D. Cerebrospinal fluid does not contain ABO antigens.