Immunology: Innate and Adaptive Immunity

what is innate immunity?

A variety of mechanisms that can prevent infection or eliminate
a pathogen

what type of immunity is present in all individuals at all times?

innate immunity

what type of immunity is the earliest response to infection (minutes/hours)?

innate immunity

what type of immunity recognizes groups of similar pathogens (not-antigen-specific)?

innate immunity

what type of immunity does not increase with repeated exposure to a pathogen (no memory)?

innate immunity

what are examples of innate immuntiy: mechanical barriers?

• skin/mucosa

• movement of mucus by cilia

what are examples of innate immuntiy: biologically active substances?

• Anti-microbial proteins (skin, mucosa)

• Cytokines (IL-1, IL-6, TNF and others)

• Acute phase proteins: C-reactive protein (CRP) and others

• Activation of Complement proteins (Alternative and Lectin Pathways)

what are examples of innate immuntiy: cellular?

• Activation of leukocytes (white blood cells):

  • Macrophages (M)

  • Neutrophils

  • Natural killer cells (NK cells)

  • Mast cells and Basophils

  • Eosinophils

  • Dendritic cells (DC)

what are the phagocytic cells that are present in most tissues?

macrophages

macrophages are derived from…?

blood monocytes

what are the major functions of macrophages?

• Phagocytosis of microbes and dead cells

• Antigen-presentation to T Cells (Discussed later)

macrophage

what are the phagocytic cells in the blood?

neutrophils (aka polymorphonuclear neutrophils)

what are the major functions of neutrophils?

Neutrophils enter infected tissues to engulf and kill extracellular pathogens, especially bacteria via phagocytosis and cytotoxic mechanisms (also in pus)

neutrophil

neutrophil eating staphylococcus

Macrophage eating M. tuberculosis

what are the cytotoxic cells that kill parasites that are too large to be ingested by phagocytes?

eosinophils

what are the major functions of eosionphils?

• Eosinophils enter infected tissues from the blood

• Killing of antibody-coated parasites via release of substances that are toxic to helminths

Eosinophils are especially important in…?

allergy, severe asthma, eczema (atopicdermatitis)

what cells are involved in responses to parasites and allergy?

mast cells and basophils

where are mast cells found?

in connective tissues throughout the body

where are basophils found?

in blood and have similar function as mast cells

what are major functions of mast cells and basophils?

• Release of granules containing histamine etc.

• Especially import for helminths

what cells remove tumor cells and infected cells?

natural killer cells

what are major functions of natural killer?

Can kill some virus-infected cells and some tumor cells via cytotoxic mechanisms

what are the major functions of dendritic cells?

• Secrete cytokines that activate innate responses (Il-1, IL-6, TNF)

• Antigen presentation to T cells

dendritic cells are referred to as ______ of the immune response

sentries

Dendritic cells (DC) are found in tissues and function to…?

detect infection and elicit innate and adaptive responses

HOW DOES THE BODY DETECT INFECTION?

Innate receptors recognize non-self structures that are
essential elements of pathogens

Innate immune cells have receptors for pathogens. These receptors are called ….?

pattern recognition receptors (PRR)

pattern recognition receptors (PRR) recognize structures called

pathogen associated molecular pattern (PAMP)

what’s an example of pattern recognition receptors (PRR) and pathogen associated molecular pattern (PAMP)?

dendritic cells and macrophages are activated when TLR-4 (toll-like receptor 4) recognizes lipopolysaccharide (LPS) from
Gram-negative bacteria.

how many pattern recgoition receptors do we know of?

a few dozen

When innate responses are not enough, dendritic cells (DC) elicit _________ responses

adaptive

WHAT WOULD HAPPEN IF A MICROBE WAS ABLE TO AVOID PRR DETECTION?

If a microbe avoids pattern recognition receptor (PRR) detection, it may evade the innate immune response, potentially leading to unchecked infection and increased virulence

walk through this diagram

what is adaptive (acquired) immunity?

Defenses mediated by the clonal expansion and differentiation
of antigen-specific lymphocytes (B cells and T cells)

IF YOU ARE VACCINATED TODAY FOR EBOLA, WILL
YOU BE PROTECTED TOMORROW?

no. it takes time (12-18 days to a month depending on the infection)

what type of immunity requires sensitization by antigen (Ag)?

adaptive (acquired) immunity

what is an antigen?

“Antigen” is what we call the foreign substance (usually a microbe) that is recognized by lymphocytes

what type of immunity develops over days/weeks?

adaptive (acquired) immunity

what type of immunity has a response that is antigen-specific?

adaptive (acquired) immunity

what type of immunity results in immunological memory?

adaptive (acquired) immunity

adaptive immune response can be classified as:

humoral immunity

cell-mediated immunity (CMI)

what is humoral immunity?

mediated by antigen-specific antibodies produced by activated B lymphocytes (B cells)

what type of immunity is this?

humoral immunity

what is cell-mediated immunity (CMI)?

mediated primarily by antigen-specific T lymphocytes (T cells)

what type of immunity is this?

cell-mediated immunity (CMI)

prime-boost antibody response to tetanus vaccination

what is the central paradigm of immunology?

clonal selection

Antigen-specific lymphocytes develop _______of exposure to antigen

before and independent

Antigen binds ________ and activates these cells to proliferate and form greatly expanded clones of antigen-specific ______ lymphocytes and ______ lymphocytes.

pre-existing antigen-specific lymphocytes

effector, memory

what is clonal deletion?

Lymphocytes that are specific for “self-antigens” are eliminated

Each lymphocyte clone has receptors that recognize…?

one specific antigen

what is clonal selection?

Proliferation and differentiation to produce effector cells and memory cells (both T and B cells)

what are the primary lymphoid organs? (where B and T cells develop in absence of antigens)

Bone Marrow (B cell development)
Thymus (T cell development)

what are the secondary lymphoid organs? (where B and T cells go and wait for exposure)

Adenoid
Tonsil
Lymph nodes
Spleen
Peyer’s patches

what does it mean that antibody responses are polyclonal?

Polyclonal antibody responses involve the production of multiple antibody types by different B cell clones, each targeting the same antigen.

what does it mean that antibody binds to an epitope?

An antibody binds specifically to a distinct part of an antigen known as an epitope

what is this called?

Ag-Ab complex (immune complex)

do u have lymphocytes (both B and T cells) that have antigen-specific receptors for tetanus toxin?

yes

do you have serum antibodies specific for tetanus toxin?

yes (because we’ve been vaccinated)

do u have lymphocytes (both B and T cells) that have antigen-specific receptors for Ebola toxin?

yes

do you have serum antibodies specific for Ebola virus?

no (because you need exposure to antigen)