Introduction to Blood and Immune

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36 Terms

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Blood components

Plasma - water and dissolved substances (55%)

White blood cells + platelets

Red blood cells (45%)

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Cellular components of blood

  • Red blood cells

  • White blood cells

  • Platelets

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Red Blood Cells

are cells that carry oxygen

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White blood cells

are cells that fight infection

  • Neutrophils

  • lymphocytes ( B + T cells)

  • monocytes

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Immune system

  1. differentiate between self and non-self

  2. seek and destroy non-self, pathogens + bacteria

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Pathology

the study of diseases and how they progress

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Pathogen

something that causes a disease, for example bacteria or virus

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Immune system

a system of defences to stop invading pathogens

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Immunogenic

something which induces an immune response in the body, this can be a humoral (antibody) and/or cell-mediated immune response

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Antigen

a molecule which induces an immune response via a lymphocyte. Pathogens have many antigens on their surface

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Antibody

a molecular component of the immune system that recognises and binds (interacts with) antigens

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Innate immunity

  • Always deployed

  • Ready to be quickly deployed

  • First and second line of defense

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Adaptive immunity

  • Activated by exposure to specific pathogens

  • Third line of defense—internal adaptive defense s

  • Consists of lymphocytes B cell and T cells

  • Antibodies

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The lymphatic system is involved in…

internal innate immunity and adaptive immunity, lymph nodes

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External innate defences

Barrier defences

  • Skin

  • Mucous and mucous membranes

  • bodily secretions

All pathogens must get around these barriers to gain access to body

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Internal innate defences

Second line of defense

  • Phagocytic cells engulf pathogens

  • Vasodilation + increased permeability of blood vessels

  • Blood cells leave blood vessels + enter injury site causing redness, heat, swelling

  • Natural killer cell recognition + killing of virus infected

  • Clean up and repair

  • Not pathogens specific, immune cell based responses

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Inflammation

  1. Tissue injury; release of chemical signals such as histamine (dilate blood vessels)

  2. Dilation and increased leakiness of local blood; migration of phagocytic cells to the area from blood vessels, blood clots and swelling

  3. Phagocytic cells engulf bacteria and cell debris; tissue heals

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Phagocytosis

Performed by phagocytes e.g. neutrophils, monocytes/macrophages

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What happens first when injured?

  • Tissues cells damaged by the wound

  • Damaged cells release chemicals - histamines

  • Histamine makes the nearby blood vessels get leaky - fluid enters nearby tissues causing swelling

  • Fluid includes factors to assist with healing and clotting

  • Phagocytic cells are activated, recognise and engulf bacteria

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Internal adaptive defenses

Third line of defence

  • Lymphocytes - B and T cells

  • This immune response is generated in the lymphatic system and carried out all over the body

  • Lymphocyte B cell produces antibodies

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B cells

Develop and specialise in the bone marrow

Makes antibodies

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T cells

Develop in bone marrow and mature in the thymus

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How are B and T cells activated?

Activated by exposure to specific pathogens

Specific shapes of receptors detect specific pathogens ‘lock and key’

Born with a massive repertoire of B and T lymphocytes — high variety means more likely to be able to recognise several varieties of pathogens

Each lymphocyte represents a different antigen

Specificity randomly produced by rearrangement of genes coding for the B cell and T cell antigen receptors

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Antigens have 2 important characteristics:

  1. Immunogenicity

  2. Reactivity

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Immunogenicity

The ability to provoke an immune response by stimulating the production of antibodies of T cells

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Reactivity

The ability of the antigen to react specifically with the antibodies or cells it provoked

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Most antigens have several…

Epitopes that are recognised by antibodies or T cells

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Antigen recognition activates lymphocytes to undergo…

‘clonal expansion’ that mediate adaptive immunity

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What provides basis for infection induces immunity and vaccination?

  • Memory B (and T) cells can live for decades in lymph node

  • Activated if the body is exposed a scone time to same pathogen

  • Secondary response much faster, stronger, lasts longer than first

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What happens if immediate response doesn’t deal with all bacteria?

  • Bacteria grows rapidly, 20m doubles—infection spread

  • Phagocytes that engulfed bacteria during innate system will ‘advertise’ antigen

  • T cells can recognise antigen amd ‘help’ B cells - amplify response, clone and pump antibodies binding to bacteria

  • B-cells will clone themselves, produce antibodies, and save a copy of themslevs for future infections (memory B cells)

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Antibodies are important markers of _______ + ______

previous infection + immunity

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_______ and ___/___ are the ______ antigens and most commonly used in serology

Nucleocapsid, Spike/RBD, immunodominant

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Applications of antibody assays

  1. Detect historical infections

  2. Estimate prevalence

  3. Understand persistence and protection

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Neutralising antibodies

  • RBD (receptor binding domain) of spike protein binds to ACE2 receptor to infect human cells

  • Nabs (neutralising antibodies) bind to the RBD and block tehre interaction (with ACE2) - virus is now unable to enter cells

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Serology for indiviudal

Antibody test provides data on a single persons’ infection or vaccine history

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Serology for population (serosurvey)

The collection and testing of blood from a defined population population to estimate the prevalence of antibodies against an infectious pathogen as an indicator or exposure