PengantarImunologi adalah ilmu yang mempelajari tentang imunitas atau kekebalan akibat adanya rangsangan molekul asing dari luar maupun dari dalam tubuh hewan atau manusia, baik yang bersifat infeksius maupun non infeksius.
Imunitas : Daya tahan tubuh untuk melawan penyakit melawan infeksi.
Semua sel dan molekul yang terlibat dalam imunitas tubuh, merupakan suatu kesatuan fungsional disebut :sistem imun.
Tanggap (respon) terhadap substansi asing yang masuk ke dalam tubuh, secara kolektif disebut respon imun .
Definisi spesifik :Imunitas adalah reaksi untuk melawan substansi asing yang masuk ke dalam tubuh seperti mikroorganisme (bakteri, virus, parasit) & molekul besar (protein, polisakharida). Reaksi yang terjadi meliputi reaksi seluler dan molekul.
DefenisiSel imunokompeten yaitu semua sel yang berfungsi dalam respon imunSel yang mampu membedakan sel tubuh dengan zat asing dan menyelenggarakan inaktivasi atau perusakan benda-benda asingSemua sel ini berasal dari sel induk pluripoten yang kemudian berdiferensiasi melalui 2 jalur
*Sel dlm Sistem Imun
PERKEMBANGAN LEUKOSIT DARI SEL PLURIPOTEN
A. Immunocompetent cells in general1. T-cells T cells express T-cell receptors that recognize the antigen information associated with MHC molecules. Produced in the bone marrow and develop in the thymus. T cells are classified by function into CD4 positive helper T cells (helper T lymphocyte; Th) and CD8 positive cytotoxic T lymphocytes (Tc). Th contains CD4 on the cell surface, by which Th adheres to MHC class II. Therefore, Th reacts against antigen-presenting cells and B cells, which contain MHC class II. Th differentiates into subtype Th1 or Th2, depending on the surrounding cytokine environment. Th1 secretes cytokines such as IL-2 and IFN-g , activating histiocytes (macrophages) primarily, and it induces cellular immunity by evoking various inflamatory reactions.
..contTh2 secretes IL-4 and IL-5, activates antibody production in B cells, and inactivates foreign substances (humoral immunity). It is known that Th1 is involved mostly in type IV allergy while Th2 is involved in type I allergy (atopic diseases). Tc contains CD8, by which Tc is associated with MHC class I to initiate cytotoxic immunity; in this way, non-self cells and virus-infected cells are destroyed. Tc is important in transplantation immunity, tumor immunity and viral infections. Recently, the presence of another subtype regulatory T cell (Treg) has been identified. Treg is considered to be involved in immune control, including suppression of autoimmune disease onset. It is also known that some Th and Tc circulate in the blood after an immune reaction to guard against re-infection.
2. B cellsB cells derive from hematopoietic stem cells in the bone marrow, after which they differentiate. They react against foreign antigens in lymphnodes, the spleen, and peripheral tissues to differentiate into antibody-forming cells (plasma cells); B cells produce antibodies in this process. B cells contain MHC class II and activate T cells as antigen-presenting cells. Immunoglobulins expressed on the surface of B cells react to the corresponding targeted antigens to convey information to T cells.When activated, most of the B cells differentiate into antibody producing cells that provide antibodies against the antigens and die in the course of time except for some that differentiate into memory B cells so that they are able to produce antibodies immediately upon reinfection.
3. Histiocytes (macrophages)Histiocytes (macrophages) are bone marrow-derived cells that have intense phagocytic reactivity. There are dermal-originated histiocytes and monocytes circulating in the blood. Histiocytes degrade phagocytosed antigen proteins into peptides and present the antigen information to T cells by MHC class II. In inflammation, histiocytes proliferate, migrate to loci, leave various cytokines, and induce phagocytosis of causative factors and injure the infected cells. Histiocytes may fuse to form enlarged cells. They are the main cells to form granulomas in chronic inflammation
*Mechanism of Phagocytosis
4. Mast cellsMast cells play a central roll in type I allergy. They contain high-affinity IgE receptors (FceRI) and considerable amounts of histamines. When binded with IgE and further cross-linked by an antigen to react to IgE, mast cells are activated to release inflammatory cytokines that lead to dermal edema in erythema or urticaria. Mastcytosis is caused by tumorous proliferation of mast cells.
5. EosinophilsEosinophils have phagocytic and cytotoxic functions. Associated with atopic diseases (type I allergy), autoimmune blistering diseases, and parasitic infections. Activated by Th2-derived IL-5. Morphologically, they are characterized by having multiple eosinophilic granules. They do not usually exist in normal skin.
6. NeutrophilsNeutrophils are phagocytic and play a large role in fightingbacterial infections.They are hardly ever found in normal skin. They are also activated in inflammatory diseases. Neutrophilic infiltration (pustule) is observed in psoriasis vulgaris and Sweets disease.
7. BasophilsLike eosinophils and neutrophils, basophils are also granular leukocytes, and they contain multiple basophilic granules. They contain histamines in the granules and have FceRI on the surface.They are involved in type I allergy. The functions of basophils are similar to those of mast cells.