免疫学学习笔记-2

Cells of the immune system

Leukocytes - white blood cells (WBCs)

·Arise from bone marrow

·Found in blood and lymph 淋巴

·Also known as immune cells

Part 1 Granulocytes  

Leukocytes

·Granulocytes            粒细胞

·Agranulocytes      无粒细胞

Granulocytes

·Irregularly shaped nuclei with two or five lobes

·The granules of these cells stain different colors

Granulocytes

·Basophils            嗜碱性粒细胞（是最少见的粒细胞，约占白细胞总数的0.5-1%。它们在过敏反应和炎症反应中起作用，释放组胺和肝素等物质。）

·Eosinophils      嗜酸性粒细胞（约占白细胞总数的1-4%。它们主要参与过敏反应和抗寄生虫感染。）

·Neutrophils      中性粒细胞（最常见的粒细胞，约占白细胞总数的50-70%。它们的主要功能是吞噬和消灭病原体，特别是细菌。）    

Basophils      嗜碱性粒细胞

·Heavily granulated cytoplasm      重颗粒状细胞质

·Granules stain blue-purple with basic dye methylene blue            用碱性染料亚甲蓝将颗粒染成蓝紫色

·The granules of basophils contain vasoactive mediators e.g. histamine, leukotriene 血管活性介质            组胺      白三烯

·Play role in inflammation and allergic responses

·Relatively rare in circulation

Eosinophils      嗜酸性粒细胞

·Two-lobed (bi-lobed) nucleus      两叶（bi-lobed）核

·Granules stain red or orange with acidic dye eosin red      颗粒被酸性染料曙红染成红色或橙色

·Motile phagocytic cells 运动吞噬细胞

·Provide defense against protozoan and helminthic parasites      防御原生动物和蠕虫寄生虫

Neutrophils      中性粒细胞

·Nucleus has three to five lobes (multi-lobed nucleus)

·Granules stain readily by neutral dyes i.e. they stain neutral pink  颗粒很容易被中性染料染色，即它们染成中性粉红色

·Also known as polymorphonuclear (PMN) neutrophil 也称为多形核 (PMN) 中性粒细胞

·Most abundant leukocytes in blood (50-70%) 血液中最丰富的白细胞（50-70%）

·Active phagocytic cells

·The granules are of three types:    

oPrimary granules (larger, denser)

oSecondary granules

oTertiary granules

·First cells to migrate at the site of infection but do not provide prolonged defense

·Life span of few days

Mast cells      肥大细胞

·An indented nucleus 凹进的核

·Cytoplasm filled with granules that contain vasoactive mediators 细胞质充满含有血管活性介质的颗粒

·Mature mast cells are found in tissues e.g. skin, mucosal surfaces, connective tissues of organs 成熟的肥大细胞存在于组织中，例如皮肤、粘膜表面、器官结缔组织

·Play role in inflammation and allergic responses 在炎症和过敏反应中发挥作用

Part 2 Agranulocytes  

Leukocytes

·Granulocytes            粒细胞

·Agranulocytes      无粒细胞

Agranulocytes

·One-lobed nucleus

·Mononuclear leucocytes

·Cytoplasm appears uniform under light microscope 光学显微镜下细胞质显得均匀

Agranulocytes

·Monocytes      单核细胞（约占白细胞总数的2-8%。它们在组织中分化为巨噬细胞和树突状细胞，负责吞噬病原体和清除细胞碎片，同时在免疫反应中作为抗原呈递细胞。）

·Lymphocytes      淋巴细胞（约占白细胞总数的20-40%。它们在适应性免疫反应中起重要作用，分为B淋巴细胞（产生抗体）和T淋巴细胞（杀死受感染的细胞和调节免疫反应）。）

Monocytes

·Single slightly lobed nucleus

·Largest type of leucocytes

·Their cytoplasm contains lysosomes, phagocytic vacuoles 吞噬泡

·Circulate in blood

·Migrate into tissues, where they differentiate into macrophages

Macrophages

·Large white blood cell

·Resident in almost all tissues

·Relatively long-lived cells

·Locate, engulf and destroy microbes (phagocytosis)

·Two types:

oFree Macrophages

§Motile 运动型

§Roam the tissues and gather at sites of infection or inflammation在组织中游走并聚集在感染或炎症部位

oFixed Macrophages

§Resident in some tissues and organs of the body

§They are given special names, e.g.

Dendritic cells

·Star-shaped morphology

·Refers to their branched appearance

·Present in skin and mucous membranes 粘膜

·They are a special group of Phagocytes

·Perform antigen capture and antigen presentation in adaptive immunity

Lymphocytes

·The main type of cells found in lymph, hence their name 淋巴

·All lymphocytes arise in bone marrow

Natural killer lymphocyte

·Large lymphocytes

·Have a distinctive granular cytoplasm

·Non-phagocytic cells

·Attack and kill infected or cancerous body cells by secreting toxins onto their surfaces 癌变的

Small lymphocytes: B cells and T cells

·Smallest leukocytes

·Contain large, round, central nucleus surrounded by a thin rim of cytoplasm 含有大而圆形的中央核，周围有薄薄的细胞质边缘

B Lymphocyte vs. T Lymphocyte

·They are distinguished by surface proteins which are integrated in their cell membrane

·Some proteins act as antigen receptors

·B cell receptor (BCR)       T cell receptor (TCR)    

B Lymphocyte

·B cell

·Mature in bone marrow

·Circulate in blood

·Disperse into various lymphoid organs where they become activated分散到各种淋巴器官中并在那里被激活

·Their cell surface antigen receptors are known as B-cell receptors (BCRs).

· Mature, activated B cell is called a Plasma cell. 浆细胞

· Plasma cell produce and secrete Antibodies.

· Naïve B cell à plasma cell à antibodies

Antibodies

·Antibodies are soluble proteins which are secreted by plasma cells.

·They bind to specific antigens.

·Antibodies have a basic Y shaped structure.

T Lymphocyte

·T cell

·Mature in an organ called thymus.

·Their cell surface antigen receptors are known as T-cell receptors (TCRs).    

Part 3 Natural Killer (NK) Cells  

Natural killer lymphocyte

·Large lymphocytes

·Non-phagocytic cells

·The granules of NK cells contain preformed biologically potent molecules.

NK 细胞颗粒含有预先形成的具有生物活性的分子。

·Play role in defense against both intracellular and extracellular pathogens.

Defense against intracellular pathogens - Toxic proteins (cytotoxins):

1)Perforin: inserts into the plasma membrane of the target cell and create perforations in the membrane. This leads to cytolysis. 穿孔素：插入靶细胞的质膜并在膜上产生穿孔。这导致细胞溶解。

2)Granzyme: induce target cell to undergo apoptosis. 颗粒酶：诱导靶细胞凋亡。

Defense against extracellular pathogens – NK cells secrete IFN-γwhich act as Macrophages Activation Factor