immune cells

Immune cells:
The human immune system consists of a complex and dispresed set of freely movable cells arise from haematoboietic stem cells(HSC).The pluripotent HSC in bone marrow gives rise to all leukocytes ,erythrocytes,and platelets.
Granulocytes (PMNs):
Neutrophils:
Eosinophils:
Basophils/Mast cells:
Monocytes/Macrophages System:
Phagocytosis:
Dendritic cells (DC):
Lymphocytes:
T lymphocytes:1-It comprises 70-80% of all circulating lymphocytes.
2-Thymus –derived lymphocytes.
3-No surface immunoglobulins.
4-Detect the foreign Ag by T-cell receptor (TCR),which is composed of (a)pair of transmembrane proteins (? & ?) in 95% T cells pool or (? & ? )in 5% ,and (b)CD3 complex
5-Have long lived time ,as compared with B cells.
6-Can only recognize Ag if it is presented by APCs.
7-Release soluble mediators; cytokines, that regulate the function of other immune cells.
Subdivision of T cells:
1-Helper Tcells (TH cells ):It comprises 70-75 % o fthe toteal T cells,carry CD4 ,and interact with MHC II on APCs.Two types of TH cells:
A-TH1 cells:Regulate the cell mediated immunity .They are essential for controlling of intracellular parthogens(viruses, mycobacteria,Listeria,..)by producing IFN-? ,which activates macrophages .
B-TH2 cells:Regulate humoral immunity that eliminates the extracellular infections and toxins,which unlike intracellular pathogens are exposed to Ab in blood and other body fluids.TH2 cells produce IL-4, and IL-5,which act as B-cells activating factors.
In AIDS,the HIV attacks CD4-bearing T cells(TH cells) and reduce the number of these cells.This condition causes the immunodeficiency and makes the patients highly susceptible to infections.
2-Cytotoxic Tcells(CTLs):Comprise 25-30 % of total T cells , have CD8 and interact with MHC I expressed on target cells.They can kill:virus- infected cells,cells -infected with intracellular pathogens ,allograft,and cancer cells.
Mechanism of cytotoxicity:
CTLs produce (a)perforin : a serine protease that form 10-20 nm pores in the plasma membrane of the target ,in a manner similar to that of MAC.These pores function as means for(b)granzymes ,which induce cell death of the target by triggering apoptosis.
3-Regulatory(suppressor) T cells :Suppress activsation of the immune system after recovery of the infection and maintain immune homeostasis.Most of them are CD4 marker.
B cells:
Memory cells:
Natural killer (NK) cells :