RBCs, unlike nucleated cells, aer more sensitive to complement mediated cell lysis. Explain why?

SouravSeptember 4, 2024

Answer

Red blood cells (RBCs) are more sensitive to complement-mediated cell lysis compared to nucleated cells due to several reasons related to their structure and function:

1. Lack of Protective Mechanisms:
   • Complement Regulators: Nucleated cells have various complement regulatory proteins on their surfaces, such as CD55 (decay-accelerating factor) and CD59 (protectin), which protect them from complement-mediated damage. These proteins inhibit complement activation and prevent the formation of the membrane attack complex (MAC) that leads to cell lysis. RBCs have fewer of these protective mechanisms, making them more susceptible to complement-mediated lysis.
2. Surface Composition:
   • Lipid Bilayer Exposure: The lipid bilayer of RBCs is relatively exposed compared to nucleated cells, which have more complex and thicker plasma membranes. This exposure makes it easier for complement components to bind and form the MAC, leading to cell lysis.
3. High Density of Complement Receptors:
   • Complement Receptors: RBCs have complement receptors (such as CR1) that can bind complement fragments (e.g., C3b). When these receptors are engaged, the complement cascade can be activated more readily, leading to increased susceptibility to complement-mediated lysis.
4. Absence of Nucleus:
   • No Nucleus: RBCs lack a nucleus and other organelles, which means they do not have the intracellular machinery to repair damage or counteract complement-induced injury. Nucleated cells, with their complex internal structures, can better manage and repair complement damage.
5. Limited Repair Mechanisms:
   • Reduced Repair Capabilities: RBCs have limited repair mechanisms because they do not have the capacity to synthesize new proteins or regenerate damaged components. Once the RBC membrane is compromised by complement attack, it is less able to recover compared to nucleated cells.