Question

A young female college student develops a cough and diarrhea with an elevated respiratory rate and high temperature. She also had enlarged tonsils. She has been having similar symptoms on a regular basis. After some blood work on this patient, it was determined that this patient, along with her sisters, had a deficiency in C8 protein.

1. What is the role of the C8 protein?
2. What is the ultimate goal of the terminal phase (membrane attack complex) of the complement cascade?
3. How can this deficiency be beneficial to a blood product recipient?
4. What impact would this deficiency have on bacteria?

Answer 1

A. C8-binding protein is an intrinsic membrane protein of the human erythrocyte. It inhibits the complement (C5b-9)-mediated lysis in a species-restricting manner. Complement component 8 deficiency is a disorder that causes the immune system to malfunction, resulting in a form of immunodeficiency. Immunodeficiencies are conditions in which the immune system is not able to protect the body effectively from foreign invaders such as bacteria.

2. The membrane attack complex (MAC) or terminal complement complex (TCC) is a structure typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is one of the effector proteins of the immune system. The membrane attack complex (MAC) forms transmembrane channels. These channels disrupt the cell membrane of target cells, leading to cell lysis and death.

C. In the absence of C-8 complement system the bloos can be easily taken from donr and the antibody will not form against the donor's RBCs.

D. People with complement component 8 deficiency have a significantly increased risk of recurrent bacterial infections, particularly by a bacterium called Neisseria meningitides. Infection by this bacterium causes inflammation of the membranes surrounding the brain and spinal cord (meningitis).