Presentation is loading. Please wait.

Presentation is loading. Please wait.

Cells of the Immune System and Antigen Recognition Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586

Similar presentations


Presentation on theme: "Cells of the Immune System and Antigen Recognition Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586"— Presentation transcript:

1 Cells of the Immune System and Antigen Recognition Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone:

2 Teaching objectives To review the role of immune cells in protection from different types of pathogens To discuss the types of cells involved in immune responses To describe the nature of specificity in adaptive immune responses To understand the role of lymphocyte recirculation in immune responses

3 Overview of the immune system Purpose: – Protection from pathogens Intracellular (viruses, some bacteria and parasites) Extracellular (most bacteria, fungi, and parasites) – Eliminate modified or altered “self” Cancer or transformed cells Sites of action: – Extracellular – Intracellular

4 Overview- extracellular pathogens Ab are primary defense – Neutralization – Opsonization – Complement activation

5 Overview- intracellular pathogens Cell-mediated responses are primary defense – Ab are ineffective – Two scenarios: Pathogen in cytosol – Cytotoxic T cell (CD8) Pathogen in vesicles – Th1 (CD4) releases cytokines – Activates macrophages

6 Cells of the immune system Immune systemMyeloid cellsGranulocytic Neutrophils Basophils Eosinophils Monocytic Macrophages Kupffer cells Dendritic cells Lymphoid cellsT cells Helper cells Suppressor cells Cytotoxic cells B cellsPlasma cellsNK cells

7 Development of the immune system NK cell Stem cell Macrophage Lymphoid progenitor Myeloid progenitor T cell B cell Plasma Cell Granulocyte Monocyte Mast cell Dendritic cell

8 Cells of the immune system GranularAgranular (35% in circulation) Basophil Eosinophil Plasma cell Lymphocyte (T, B, NK) NeutrophilDendritic cell Monocyte

9 Phagocytosis and Intracellular killing Neutrophils and Macrophages

10 Phagocytes – neutrophils (PMNs) Characteristic nucleus, cytoplasm Granules CD66 membrane marker protein Geimsa stain Source: Neutrophil

11 Characteristics of neutrophil granules Primary granulesSecondary granules Azurophilic; young neutrophilsSpecific for mature neutrophils Contain: cationic proteins, lysozyme, defensins, elastase and Contain: Lysozyme, NADPH oxidase components and myeloperoxidaseLactoferrin and B12-binding protein

12 Phagocytes – macrophages Characteristic nucleus lysosomes CD14 membrane marker protein Macrophage Source: Dr. Peter Darben, Queensland University of Technology, used with permission

13 Non-specific killer cells NK cells Eosinophils

14 Natural killer (NK) cells Also known as large granular lymphocytes (LGL) Kill virus-infected or transformed cells Identified by the CD56+/CD16+/CD3- Activated by IL-2 and IFN-γ to become LAK cells

15 Eosinophils Characteristic bi-lobed nucleus Cytoplasmic granules, stain with acidic dyes (eosin) – Major basic protein (MBP) – Potent toxin for helminths Kill parasitic worms Source: Bristol Biomedical Image Archive, used with permission

16 Mast cells Characteristic cytoplasmic granules Responsible for burst release of preformed cytokines, chemokines, histamine Role in immunity against parasites Source: Wikimedia

17 Cells of the immune system: innate Phagocytes – Monocytes/macrophages – PMNs/neutrophils NK cells Basophils and mast cells Eosinophils Platelets

18 Cells of the immune system: APC Cells that link the innate and adaptive arms – Antigen presenting cells (APCs) Heterogenous population with role in innate immunity and activation of Th cells Rich in MHC class II molecules (lec 11-12) – Examples Dendritic cells Macrophages B cells Others (Mast cells)

19 Cells of adaptive immune response T cells and B cells

20 Cells of the immune system: adaptive Lymphocytes – B cells Plasma cells (Ab producing) – T cells Cytotoxic (CTL) Helper (Th) – Th1 – Th2 – Th17 – T-reg

21 Major distinguishing markers MarkerB cellCTLT-helper Antigen RBCR (surface Ig)TCR CD3--++ CD4-- + CD8--+ CD19/ CD20+-- CD40+--

22 Specificity of adaptive immune response Resides with Ag R on T and B cells TCR and BCR – both specific for only ONE antigenic determinant TCR is monovalent BCR is divalent T cell TCR Ag B cell BCR Ag

23 Specificity of adaptive immune response Each B and T cell has receptor that is unique for a particular antigenic determinant on Ag Vast array of different AgR in both T and B cell populations How are the receptors generated? – Instructionist hypothesis Does not account for self vs non-self – Clonal selection hypothesis AgR pre-formed on B and T cells and Ag selects the clones with the correct receptor

24 Four principles of clonal selection Hθ 1.Each lymphocyte has a SINGLE type of AgR 2.Interaction between foreign molecule and AgR with high affinity leads to activation 3.Differentiated effector cell derived from activated lymphocyte with have the same AgR as parental lymphocyte (clones) 4.Lymphocytes bearing AgR for self molecules are deleted early in lymphoid development and are absent from repertoire

25 Specificity of adaptive immune response Clonal selection Hθ can explain many features of immune response – Specificity – Signal required for activation – Lag in adaptive immune response – Discrimination between self and non-self

26 Development of the immune system NK cell Stem cell Macrophage Lymphoid progenitor Myeloid progenitor T cell B cell Plasma Cell Granulocyte Monocyte Mast cell Dendritic cell Bone Marrow Thymus Tissues 2° Lymphoid

27 Lymphocyte recirculation Relatively few lymphocytes with a specific AgR – 1/10,000 to 1/100,000 Chances for successful encounter enhanced by circulating lymphocytes – 1-2% recirculate every hour

28 Lymphocyte recirculation Lymphocytes enter 2° lymphoid organs via high endothelial venules (HEVs) Ag is transported to lymph nodes via APC Upon activation, lymphocytes travel to tissues T cellB cell MonocyteDC APC T cell B cell T cell Bone marrow Thymus Tissues Virgin lymphocytes Spleen and lymph nodes Primed lymphocytes

29 Lymphocyte recirculation After activation, new receptors (homing R ) are expressed to direct to tissues R on lymphocytes recognize CAMs on endothelial cells Chemokines at infection help attract activated lymphocytes T cellB cell MonocyteDC APC T cell B cell T cell Bone marrow Thymus Tissues Virgin lymphocytes Spleen and lymph nodes Primed lymphocytes


Download ppt "Cells of the Immune System and Antigen Recognition Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586"

Similar presentations


Ads by Google