Problem 174 - Objective Biology for NEET

Question

Assertion: Individual with ' \(\mathrm{O}\) ' blood group is considered to be universal donor. Reason: Blood of 'O' blood group individual do not contain antigens on their RBCs.

Step-by-Step Solution

Answer

The assertion is correct. Individuals with blood group O can donate to any blood group because their RBCs do not have A or B antigens, so there is no risk of an immune response triggered by the recipient's body recognizing foreign antigens.

Step 1: Understanding Blood Antigens

Antigens are substances that the body recognizes as foreign, and triggers an immune response. In the context of blood groups, there are A and B antigens, and the presence or absence of these on red blood cells (RBCs) determines a person's blood type. For example, blood type A has A antigens, B has B antigens, AB has both, and O has none.

Step 2: Understanding Blood Donation

In blood donation, the compatibility between the donor and the recipient's blood types is vital to prevent dangerous immune reactions. If a person with blood type A (containing A antigens) receives blood from type B (containing B antigens), their body would recognize the B antigens as foreign and produce antibodies to attack them.

Step 3: Relating Antigens to O type Blood Donation

Type O blood does not have A or B antigens on the RBCs. This means when type O blood is donated, there are no antigens to be recognized as foreign by the recipient's body, regardless of their blood type. Hence, individuals with blood type O can donate blood to any other blood group - A, B, AB or O, and for this reason, are considered 'universal donors'.

Key Concepts

Universal Donor

The term "Universal Donor" is used primarily in blood donation contexts to describe individuals with a particular blood type that can be safely given to people of all other blood types. People who belong to the O negative blood group are most commonly referred to as universal donors. This is because their red blood cells (RBCs) lack A and B antigens, which are normally present on RBCs and could trigger an immune response in the recipient. Since O negative RBCs do not carry these antigens, they can be transfused into patients with any ABO blood type without causing an adverse reaction. This universal compatibility makes O negative blood especially valuable in emergency situations when there is no time to type-match a recipient’s blood.

Blood Donation

Blood donation is the process where a person voluntarily gives blood to be used for medical purposes. There are simple yet crucial aspects to consider when it comes to blood donation, most importantly the compatibility between donor and recipient blood types.

• Safe transfusions require that the donor blood does not contain antigens that the recipient's immune system would attack.
• For example, blood type A donors have A antigens; if their blood is given to a person with B blood type, the recipient's body will see A antigens as foreign and create antibodies to fight them.

This is why knowing your blood type and ensuring compatibility in donations is essential. It prevents potentially life-threatening immune responses.

Antigens and Antibodies

Antigens and antibodies play a central role in determining blood compatibility. An antigen is a molecule capable of inducing an immune response in the host organism. In the context of blood, there are two primary antigens, A and B, found on the surface of RBCs. The presence or absence of these antigens classifies blood into different groups.

• Type A blood has A antigens.
• Type B has B antigens.
• Type AB has both A and B antigens.
• Type O lacks both A and B antigens.

Antibodies are immune proteins that target and attach to foreign substances such as antigens. This interaction is crucial during a transfusion because if donor blood contains antigens not present in the recipient's blood, the recipient's antibodies will perceive them as a threat and mount an immune response, potentially leading to severe complications.

Red Blood Cells (RBCs)

Red Blood Cells (RBCs) are fundamental in the context of blood types and transfusion compatibility. RBCs carry oxygen from the lungs to the body's tissues and return carbon dioxide back to the lungs for exhalation. These cells possess specialized structures called antigens on their surface.

• The two most significant RBC antigens in blood transfusions are A and B.
• The presence or absence of these determines your ABO blood type.
• In transfusions, it’s essential that donor RBCs do not present antigens that could be harmful to the recipient.

RBCs' lack of A and B antigens in O type people means that this blood group is unique. It allows them to donate blood across all blood types without risking antigen-antibody reactions, making them universal donors in urgent medical cases.