Biomedical Engineering Reference
In-Depth Information
108
Light chain
214
N
COOH
Heavy chain
N
COOH
446
113
N
COOH
Heavy chain
N
COOH
Light chain
Variable (V)
regions
Constant (C)
region
= Hypervariable region
= Hinge region
= Carbohydrate
= Disulide bridge
FIGURE 22.4
This image represents the polypeptide chain structure of a molecule of IgG. The numbers
indicate the number of amino acids. In the actual molecule, the chains are folded so that each cysteine is
brought close to the partner with which it forms a disuli de (S-S) bridge.
intracellular pathogens. NK cells are actors in antibody dependant cell-mediated cytotoxicity
(ADCC). ADCC is the killing of antibody coated target cells by immune cells with FC receptors
that recognize the C-region of the bound antibody. NK cells have the Fc receptor CD16a or FC
γ
IIIa
on their surface to facilitate the recognition.
22.3 DISEASES OF THE IMMUNE SYSTEM
Malfunction of the im mune system will result in pathological consequences such as transplant rejec-
tion, autoimmune disease, or allergy. These situations are accompanied by inl ammation that leads
to tissue damage. Individuals may also be immunodei cient (lacking a component of the immune
system) and have an increased susceptibility to infections and cancer; one such example is HIV
(decrease in the number of CD4
+
T cells).
22.3.1 A
UTOIMMUNE
D
ISEASES
Adaptive immune responses are sometimes elicited by antigens that are not associated with infec-
tious agents and this causes serious disease and tissue damage. Autoimmunity is the failure of an
organism to recognize its own constituent parts as “self,” which results in an immune response
against its own cells and tissues. Any disease that results from such an immune response is termed
as an autoimmune disease. Prominent examples include insulin-dependent diabetes mellitus type 1
(IDDM), multiple sclerosis (MS), and rheumatoid arthritis (RA).
In IDDM, the immune system attacks the beta cells in the Islets of Langerhans of the pan-
creas, destroying them, or damaging them sufi ciently to reduce and eventually eliminate insulin
production leading to hyperglycemia. The autoimmune attack may be triggered by reaction to an
infection.
In MS, the inl ammatory responses are launched in the absence of a pathogen. It seems that cer-
tain T cells by mistake recognize the insulating sheaths around nerves (myelin) as a foreign invader
