Overview
This lecture introduces the concept of blood types, focusing on the ABO and Rh systems, their importance in blood transfusions, and matching rules to prevent immune reactions.
Blood Typing Basics
- Blood type is determined by the presence or absence of specific antigens on red blood cells.
- In the ABO system, type A has A antigen, type B has B antigen, type AB has both, and type O has neither.
- Blood typing is crucial for safe transfusions due to compatibility requirements.
Transfusion Compatibility Rules
- Patients must not receive blood containing antigens they do not have.
- The immune system targets unfamiliar antigens with antibodies, causing potentially serious reactions.
- Type A individuals can only receive type A or O blood; type AB can receive any type; type O can only receive type O.
- Universal donor is type O; universal recipient is type AB.
Rh System and Other Blood Groups
- Rh system is based on the D antigen (Rh factor), resulting in Rh-positive or Rh-negative types.
- Rh-negative patients cannot receive Rh-positive blood, but Rh-positive patients can receive either.
- Each ABO type can be either Rh-positive or negative, creating 8 main blood types.
- There are over 35 blood group systems and hundreds of antigens, though ABO and Rh are most clinically significant.
Practical Considerations in Transfusions
- Most people develop strong antibodies against A, B, and D antigens.
- ABO and Rh mismatches are more common due to their prevalence in the population.
- Other antigens rarely cause problems due to their low frequency.
- Cross-matching involves mixing donor and recipient blood to check for clumping, which signals incompatibility.
Key Terms & Definitions
- Antigen — a marker molecule on red blood cells that triggers immune responses.
- ABO system — main blood group system based on A and B antigens.
- Rh factor (D antigen) — protein that determines Rh-positive or Rh-negative blood type.
- Antibody — immune protein that targets foreign antigens.
- Universal donor — type O blood, can be given to any ABO type.
- Universal recipient — type AB blood, can receive any ABO type.
Action Items / Next Steps
- Review your own ABO and Rh blood types.
- Prepare for lab or reading on blood typing and cross-matching procedures.