Problem 20 - Objective Biology for NEET

Question

ABO grouping is based on how many antigens present or absent on WBCs (a) 1 (b) 2 (c) 3 (d) None of these

Step-by-Step Solution

Answer

The correct answer is (b) 2. The ABO grouping is based on the presence or absence of two major antigens, A and B, on the surface of red blood cells.

Step 1: Understand the ABO Blood Group System

The ABO blood group system is used to denote human blood types. It is based on the presence or absence of antigens (specifically A and/or B) present on the surface of red blood cells. People can have A, B, both (which forms the AB group), or none of these antigens (forming the O group). Therefore, there are two major antigens involved in the ABO system.

Step 2: Comparing with the Given Options

Now that it's clear that the ABO system relies on two major antigens, this information can be compared with the given options. The option that matches our conclusion is (b) 2.

Key Concepts

Antigens on Red Blood Cells

Antigens are crucial molecules found on the surface of red blood cells in our body. Think of them as little flags that signal the body's immune system about the identity of the cells. In the ABO blood group system, there are specifically two important antigens known as antigen A and antigen B. These antigens determine the blood type by how they are present or absent on the red blood cells.

For instance, if red blood cells have only the A antigen, the blood type is A. If they have only the B antigen, the blood type is B. If both A and B antigens are present, the blood type is classified as AB. Interestingly, if none of these antigens are present, the blood type is O.

• Antigen A: Found in blood type A and AB.
• Antigen B: Found in blood type B and AB.
• No Antigens: Characterizes blood type O.

These antigens are significant because they affect compatibility for blood transfusions. The presence or absence of these antigens is pivotal in everyday medicine, especially when it comes to the safety and success of blood transfusions.

Blood Type Classification

The classification of blood types is a critical aspect of modern medicine, particularly using the ABO blood group system. The ABO system classifies human blood into four main types: A, B, AB, and O. This classification is based on the presence or absence of the A and B antigens on red blood cells.

Knowing your blood type is important since it helps in determining who you can donate blood to and from whom you can receive blood. For instance:

• Type A: Can donate to A and AB, and receive from A and O.
• Type B: Can donate to B and AB, and receive from B and O.
• Type AB: Can donate to AB, and is the universal recipient.
• Type O: Can donate to A, B, AB, and O, and is the universal donor.

Identifying blood types is a fundamental procedure in hospitals, ensuring the right match to prevent adverse reactions during blood transfusions. Each classification provides a lifesaving match between donors and recipients.

ABO Antigens

Within the scope of the ABO blood group system, ABO antigens play a pivotal role. These specific antigens—A and B—determine the distinct blood types within the system. Their presence or absence on red blood cells decides how the immune system will react.

The fascinating part is how these antigens serve as markers that help in the individual's immune system recognizing its own cells. The immune system, in essence, recognizes these antigens as 'self'. Conversely, if a non-matching type of blood with unfamiliar ABO antigens is introduced into the body, it can trigger an immune response. This response may result in the body attacking the foreign red blood cells.

• The presence of A antigens only: Blood type A.
• The presence of B antigens only: Blood type B.
• The presence of both A and B antigens: Blood type AB.
• The absence of A and B antigens: Blood type O.

These reactions make the understanding of ABO antigens crucial for medical procedures, ensuring that when blood is given or received, it is safe and compatible with the individual's body. This compatibility is why the ABO system is so invaluable in medical science today.