MCB3020 - Exam 4 Study Guide

What are the formed elements in blood?

the cells and cell fragments suspended in plasma

1. erythrocytes (RBCs) - transport oxygen from the lungs to the body tissues via hemoglobin

2. leukocytes (WBCs) - defend the body against infections and foreign invaders

3. platelets - aid in blood clotting; not true cells

What are the components of the first line of defense?

1. physical barriers

   • skin

   • mucous membrane

   • mucus

   • alveolar macrophages

2. chemical barriers

   • lysozyme

   • normal flora

What are the components of the second line of defense?

• phagocytosis

• inflammation

• natural killer (NK) cells

• fever

• complement system

What are the components of the third line of defense?

• lymphocytes (B and T cells)

• antibodies

• antigen-presenting cells (APCs)

Compared innate immunity and acquired immunity.

1. Innate immunity

   • immediate, nonspecific defenses

   • no memory

   • short-term

2. Acquired immunity

   • delayed but specific defenses

   • has memory

   • long-term or lifelong

Compare the epidermis (skin) and epithelium (mucous membranes) and their role in the immune system.

1. Epidermis

   • covers external surface of the body

   • tightly packed layers of cells

   • contains lysozyme, sweat, and normal flora

2. Epithelium

   • thin layer of tightly packed cells lining the internal cavities

   • traps and expels microbes via mucus and cilia

Where are all the blood components originated from?

they are produced in red bone marrow stem cells via hematopoiesis (blood cell formation)

What are the primary and secondary lymphoid organs?

1. Primary

   • bone marrow - produced all blood cells; where B cells mature

   • thymus - site of T cell maturation and selection

2. Secondary

   • lymph nodes - filter lymph to remove pathogens; detects infection

   • spleen - filters blood

How is fever produced?

• infection or injury introduces pathogens

• immune cells release pyrogens (fever-inducing molecules)

• pyrogens trigger the hypothalamus to increase the body’s temperature

What is inflammation?

• a nonspecific, second line of defense to tissue injury due to infection or physical means

• injured tissue releases inflammatory mediators that results in 5 cardinal signs

  • redness

  • warmth

  • pain

  • swelling

  • altered function

• two types of inflammation: acute and chronic

What is the complement system?

• a group of serum proteins that destroy extracellular micrboes

• chemotaxis attracts phagocytes

• membrane attack complex (MAC) puncture pathogen’s membranes, causing cell lysis

• opsonization aids phagocytes by coating pathogens

Compare the classical and alternative complement pathways.

1. classical complement pathway

   • triggered by antibodies bound to antigens

   • specific immune response (part of adaptive immunity)

2. alternative complement pathway

   • triggered directly by pathogen surfaces without antibodies

   • nonspecific immune response (part of innate immunity)

What are acute-phase response proteins in complement fixation?

• plasma proteins that bind to pathogens and initiate complement activation

• ex: mannose-binding lectin

  • triggers lectin complement pathway

What is degranulation and what cells are involved?

• the process by which certain immune cells release the contents of their granules into the extracellular space

• cells involved:

  • mast cells

  • basophils

  • eosinophils

  • neutrophils

What mediators are released during degranulation?

• histamine - increases permeability of blood capillaries

• leukotrienes - cause prolonged contraction of smooth muscles

• prostaglandins - affect smooth muscle and increase mucus secretion

What are the phagocytic cells?

• monocytes

• macrophages

• neutrophils

• dendritic cells

What are the main characteristics of macrophages?

• derived from monocytes that leave the bloodstream and enter tissues

• engulf and destroy pathogens

• present antigens to T cells (antigen-presenting cells)

• secrete cytokines

What are the main characteristics of dendritic cells?

• found mainly in tissues that contact the external environment and lymphoid organs

• antigen-presenting cells

• initiate adaptive immune responses

What is the role of lysosomes in phagocytosis?

an organelle that contains digestive enzymes that break down the engulfed particle

What are neutrophils?

• phagocytes that engulf and destroy pathogen

• release enzymes to kill microbes

What are T helper cells?

• part of the adaptive immune system

• secrete cytokines

• assist B cells in antibody production

What are cytotoxic T cells?

• kill infected or abnormal cells

• release perforin and granzymes to induce apoptosis

• form memory cytotoxic T cells

What are natural killer (NK) cells?

• recognize cells with low or absent MHC I

• kill target cells through apoptosis

Compare humoral/antibody-mediated immunity and cell-mediated immunity.

1. AMI

   • B cells and antibodies

   • controls extracellular pathogens

2. CMI

   • T cells

   • controls intracellular pathogens

What are the lymphocytes?

• B lymphocytes (B cells)

• T lymphocytes (T cells)

  • helper T cells (CD4+)

  • cytotoxic T cells (CD8+)

• Natural killer (NK) cells

What are the differences between plasma cells and memory B cells?

1. Plasma cells

   • short lived

   • produce large amounts of antibodies

   • actively fight infection

2. Memory B cells

   • long-lived

   • remember the antigen and respond faster upon re-exposure

   • remain dormant until second exposure

What does antigen-presenting mean and what are the cells involved in this process?

• the process by which certain immune cells capture and display antigens using MHC molecules

• Ex: dendritic cells, macrophages, B cells

What are the components of an antibody structure?

• Fab (fragment antigen-binding) region

  • marks antigens

  • activates nonspecific defenses

• Fc (fragment crystallizable) region

  • mediates binding to host tissue and immune cells

What are the 4 types of antibodies?

1. IgG - most abundant, long-term immunity

2. IgM - first to appear after infection, activates complement

3. IgA - mucosal protection

4. IgE - allergic reactions, least abundant

What is opsonization?

• the process by which opsonin molecules coat the microbe for destruction

• enhances phagocytosis and speeds up immune response

• opsonin: antibodies, complement proteins, mannose-binding lectin

What are the different ways macrophages recognize and phagocytize pathogens?

• pattern recognition receptors

• opsonin receptors

• scavenger receptors

Why does oxygen consumption (respiratory burst) increase during infections?

when phagocytes engulf pathogens, toxic oxygen products are produced

What is naturally acquired immunity?

• immunity gained through natural exposure to pathogens or maternal antibodies

• active immunity - through infection

• passive immunity - maternal antibodies

What is artificially acquired immunity?

• immunity gained through medical procedures/immunizations

• active immunity - through vaccinations

• passive immunity - through injection of antibodies

What are the characteristics of primary immune response?

• long latent period

• antibody levels wears off quickly

• mainly IgM

What are the characteristics of secondary immune response?

• shorter lag

• rapid antibody production

• mostly IgG

What are antigens?

• molecules that elicit an immune response

• must be a certain minimum size to be recognized (most are large, complex molecules)

• must be recognized as non-self

• can have several epitopes

What are the most antigenic molecules?

proteins

How can white blood cell counts be interpreted?

• high WBC counts indicate infections, autoimmune diseases, or side effects of medications

• High neutrophils may indicate extracellular bacteria infection

• High eosinophils may indicate allergy or parasitic worm infection

How can red blood cell counts be interpreted?

• high RBC - dehydration, heart/lung disease

• low RBC - blood loss, nutritional deficiencies

How can interferon levels be interpreted?

high interferon level - viral infection