1 / 35

Host defence

This text delves into the complexities of the host defense system in intensive care units, exploring who we are defending against—ranging from bacteria to malignancies. It outlines the innate and adaptive immune systems, detailing the structure and functions of key components like phagocytes, macrophages, and lymphocytes. The discussion also covers how pathogens breach epithelial barriers, triggering immune responses, and the systemic effects of infections. By understanding these mechanisms, we can better appreciate the body's resilience and strategize more effective treatments.

marlie
Télécharger la présentation

Host defence

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Host defence

  2. Who is the Host ?

  3. Who are we defending against in ICU ? • Bacteria • Fungi • Viruses • Parasites • Protozoa • Auto-immunity ? • Malignancy ?

  4. What is the structure of our defence system ? • Innate system ( “old school”Castle with infantry defending ) • - Castle : skin and mucous membrane • -infantry ( phagocytes ) • Adaptive system (“modern “ intelligence gathering , IT and guided missiles and smart bombs)

  5. Major components of the innate system

  6. Where does the enemy attack us ? External epithelia: External surface Wounds & abrasions Insect bites Mucosal surfaces: Airway Gastrointestinal tract Reproductive tract (Fig. 2.2)

  7. In what compartment of the body is the enemy found ?

  8. The general response to infection

  9. Stages of infection

  10. MALT ( behind the walls stands a force) • Mucosa associated lymphoid tissue • 80% of all immune cells • 3 functions : • Protect mucous membranes • Prevent uptake of foreign antigens from food • Prevent pathological responses if foreign antigens cross the mucous membrane

  11. Where does the defence start ?Castle walls

  12. If a pathogen breaches the epithelium ?Enemy over the wall • then the innate immune response begins. • The cells of the immune system determine “self” from “non-self” by recognizing molecules on the microbe surface. • Macrophages and dendritic cells are immune cells (phagocytes) that reside within the tissue. Neutrophils are phagocytes that reside in the blood but can extravagate into tissue during inflammation. • There are circulating proteins, called complement, that either kill microbes or mark them for effective phagocytization.

  13. The compliment system Complement is a system of plasma proteins that interacts with pathogens to mark them for destruction. 1. Alternative pathway : pathogen surfaces 2. Mannan binding-lectin pathway : lectin binding to pathogen surfaces 3. Classical pathway : Ag:Ab complexes Functions: phagocytosis inflammation lysis

  14. How do the phagocytes recognise the enemy ? • Through pattern recognition ( genetically programmed ) • PAMPS • Toll like receptors

  15. What do the macrophages do : release IL-1B •  • Activates vascular endothelium • Activates lymphocytes • Local tissue destruction • Increases access of effector cells •  • Fever, • production of IL-6

  16. Macrophage secret TNF-alpha •  • Activates vascular endothelium • Increases vascular permeability •  • Increased entry of IgG, complement, and cells to tissues • Increased fluid drainage to lymph nodes •  • Fever • Mobilization of metabolites • Shock

  17. Macrophage secret IL-8 •  • Lymphocyte activation • Increased antibody production •  • Fever • Induces acute-phase protein production

  18. Macrophages secret IL-12 •  • Activates NK cells • Induces the differentiation of CD4 T cells into TH1 cells

  19. Expression of selectins and ICAM

  20. Acute phase response

  21. Acute phase response • Hypothalamusincreased body temperature • Fat, muscleprotein & energy mobilization to allow increased body temperature  • decreased viral & bacterial replication & • increased antigen processing & specific immune response

  22. Interferons

  23. NK-Cell

  24. NK recognise virus infected cells

  25. Adaptive immunity ( once bitten twice shy) Antigen specific response to antigen / pathogen Key feature if this system is that subsequent exposure to the initial antigen leads to more rapid and vigorous response ( Immunological memory) T and B lymphocytes drive this response from common stem cell

  26. T and B cell response • T-cell : cellular immunity through differentiation in TH-1 ( cellular )and TH-2 pathways ( humoral) • B-cell clonal response initially producing IgM and then IgG to infections : Memory cells produced that react much faster to future threats from the same pathogen.

  27. Innate vs Adaptive immunity

  28. Thymus • Positive and negative selection of t-cells • CD-4 , CD-8 and T-killer cells emerge • Thymus continues to work in adult life especially when t-cell pool is damages as in AIDS and cancer chemotherapy

  29. Investigating Immunity • 4 Major components : • Humoral immunity • Cell mediated immunity : lymphocytes • Phagocyts and polymorphnuclear cells • Complement

  30. If we’re so good how does the enemy kill us ?

More Related