Lecture on Immune System Disorders: Cytotoxic Reactions

Type II (Cytotoxic) Reactions

Activation of the complement system, a non-specific defense mechanism.
- Drills holes in cell membranes causing cell lysis.
Involvement of IgG or IgM antibodies reacting with antigens to activate this system.
Results in cell death.

Four primary blood types: A, B, AB, O.
Blood type is determined by the presence or absence of antigens on red blood cell membranes.
- Type O: Absence of A and B antigens (universal donor).
- Type A: Presence of A antigens.
- Type B: Presence of B antigens.
- Type AB: Presence of both A and B antigens (universal recipient).
Antibodies present in plasma for opposite antigens.
- Type AB: No anti-A or anti-B antibodies (universal recipient).
- Type B: Anti-A antibodies.
- Type A: Anti-B antibodies.
- Type O: Both anti-A and anti-B antibodies.
Blood transfusion reactions occur if given wrong type, activating the complement system.

Rh stands for Rhesus, related to antigen presence on red blood cells.
Rh Positive: 85% of the population, has Rh antigens.
Rh Negative: 15% of the population, lacks Rh antigens.
- Does not develop anti-Rh antibodies unless exposed to Rh-positive blood.

Occurs when an Rh-positive father and Rh-negative mother have an Rh-positive child.
First pregnancy: No issues, but mother's exposure leads to sensitization.
Second pregnancy: Mother's anti-Rh antibodies can cross the placenta and attack fetal blood cells.
RhoGAM medication is used to prevent this.
- Administered to Rh-negative mothers to prevent antibody formation.
- Has significantly reduced morbidity and mortality.

Type II cytotoxic reactions involve antibody and antigen interactions leading to cell destruction.
Understanding blood types and Rh factors are crucial for safe blood transfusions.
Hemolytic disease of the newborn can be managed effectively with RhoGAM treatment.