Nonspecific Defenses of the Host Chapter 16
I. Introduction: Overview of host defenses A. Resistance Ability to ward off disease through body defenses 1. Nonspecific All body defenses that protect one from any kind of pathogen. Includes the first and second lines of defense. 2. Specific Defenses against specific microorganisms mediated by lymphocytes (white blood cells) and special proteins called antibodies. B. Susceptibility Lack of resistance that creates host vulnerability.
Figure 16.1 - Overview (1 of 3)
II. Skin and Mucous Membranes A. Mechanical Factors Include intact skin, keratin, lacrimal apparatus of eye, saliva, mucous with ciliary escalator, and urine.
II. Skin and Mucous Membranes A. Mechanical Factors Include intact skin, keratin, lacrimal apparatus of eye, saliva, mucous with ciliary escalator, and urine.
II. Skin and Mucous Membranes B. Chemical Factors Include sebaceous (oil) glands secretion (sebum), perspiration, lysozyme (against GPC), high acidity (ph skin = 3-5, gastric juice = 1-2). C. Normal flora compete with pathogens, establish conditions unsuitable for pathogens, produce substances harmful to pathogens. Staph on skin
Phagocytosis Ingestion of a microorganism or particulate matter by phagocytic cells. A. Formed Elements of the Blood differential count of WBCs.
B. Specific Kinds of Leukocytes: Granulocytes (3 types in the blood) Neutrophils Basophils Eosinophils Dendritic cells (found in lymph nodes, skin, etc. but not in the blood) Agranulocytes (two types in the blood) Monocytes Lymphocytes- three population that appear similar Natural Killer (NK) cells B cells T cells
B. Specific Kinds of Leukocytes: Granny can t Basophils Eosinophils Neutrophils Dendritic cells She got Agranulocytes Monocytes Natural Killer (NK)ey Bi Te
C. Action of Phagocytic Cells 1. Granulocytes migrate from blood to area of infection and are phagocytic or dump granular contents on pathogens. Eosinophils are often prominent in parasitic infections. 2. Monocytes enter tissue and become fixed macrophages and then have specific names depending on area. Examples: dendritic cells-lymph nodes; Kupffer cellsliver; Langerhans-skin 3. Granulocytes (especially neutrophils) increase the most first and then monocytes increase.
C. Action of Phagocytic Cells Macrophage engulfing rod shaped bacteria
D. Mechanism of Phagocytosis Chemotaxis, adherence, ingestion, and digestion
E. Inflammation Bodily response to cell damage characterized by redness, pain, heat, and swelling. 1. Three stages: tissue damage, vasodilation, phagocytosis. 2. Goal: destroy pathogen or limit infection, then repair damage. Fig 16.8 Process of inflammation
F. Fever One of the systemic responses to infection 1. Caused (primarily) by endotoxins released by gram-negative cell walls or viruses. 2. Endotoxins cause phagocytes to produce IL-1, which acts on the hypothalamus (body s thermostat). 3. Hypothalamus releases prostaglandins that reset the temperature of the body to a higher temperature, thus causing fever via vessel constriction and shivering. As fever breaks, vasodilation and sweating occurs, so skin becomes warm.
G. Antimicrobial Substances 1. Complement System: A set of cascading serum proteins (30 or so) that participate in lysis of foreign cells, inflammation, and phagocytosis. Outcomes: inflammation, cytolysis, opsonization (immune adherence) See overview next slide fig 16.9, 16.10
Outcomes of complement activation Figure 16.9 - Overview (1 of 5)
Cytolysis caused by complement Figure 16.10 - Overview (1 of 3)
G. Antimicrobial Substances 1. Complement System a. Classic Pathway Can assist specific immunity (complement). initiated by antigenantibody reaction
G. Antimicrobial Substances 1.Complement System b. Nonspecific activation by contact with certain complement proteins and pathogen. No antibody involved Called alternate pathway Fig 16.3 Alternate pathway of complement activation
G. Antimicrobial Substances 1. Complement System c. When macrophages digest microbes, they release a chemical to stimulate liver to make proteins (lectins) that binds to pathogen and triggers activation of complement. Called lectin pathway
G. Antimicrobial Substances 2. Interferons (INF) Antiviral proteins produced in response to viral infection. Host specific but not virus specific. a. Three types: α, β, and γ interferon b. Interferon (α and β) works by inducing uninfected cells to produce antiviral proteins (AVPs) that prevent viral replication in surrounding uninfected cells. c. γ interferon produced by lymphocytes causes neutrophils to kill bacteria d. They are host-cell-specific, but not virus-specific. Now human recombinant INFs produced by genetic engineering in bacteria. Used to treat viral infections (α for herpes, hepatitis A and B), β to slow MS
Antiviral action of alpha- and beta- interferons Figure 16.15 - Overview