Animal Physiology- Immune System A

What are the two functions of the immune system?

• Management of pathogens

• Surveillance of internal state

Pathogen

A bacterium, virus, or microorganism that causes disease

Immune Sensors (There are 3)

• Macrophages

• Mast Cells

• Sensory Neurons

What do Immune Sensors recognize? There are 2.

• PAMPs (Pathogen-Associated Molecular Patterns)

• DAMPs (Damage-Associated Molecular Patterns)

Innate Immunity

Non-specific immune agents that are the first line of response to pathogenic issues

Innate immune cells

• Dendritic Cells

• Macrophages

• Natural Killer Cells (NK)

Adaptive Immunity

Specific immune agents that are the second line of defense against pathogenic threats

Adaptive immune cells are also called…

Lymphocytes

Primary Lymphoid Tissue

Bone marrow and Thymus

3 types of secondary immune organs

• Lymph Nodes

• Lymphatic Vessels

• Spleen

What lymphocytes do we have to remember?

T Cells and B Cells

Where do T-Cells mature?

The Thymus

Where do B-Cells mature?

The bone marrow

What is the primary purpose of a B-Cell?

To produce antibodies

Cytokines

Extracellular signals that impact the immune system

Macrophages

The OG big eaters, engulf and digest pathogens and cellular debris

Toll-Like Receptors (TLRs)

Receptors that detect bacterial flagella or viral RNA and initiate a cellular response

Natural Killer Cells

Cells that recognize infected host cells and kill them

Humoral Immunity

The immune system components that are present in the blood

Cytotoxic T-Cells

Kill virus-infected or cancerous cells

Helper T-Cells

Activate memory B-Cells and cytotoxic T-Cells to mount an immune response

Important components of Humoral Immunity (there are 3)

• Antibodies (Abs)

• Antigens (Ags)

• B-Cells

Antigen (Ag)

A foreign or non-self object that is recognized by an antibody

Antibody (Ab)

A protein that recognizes a certain antigen and forces it to wear the antibody as a hat

Antigenic Determinants (Epitopes)

The site of an Antigen that an Antibody recognizes

Polyclonal Antibody

Recognizes multiple parts of the same antigen

Monoclonal Antibody

Recognizes one part of an antigen

How do B cells let us know what antibodies they’re making?

A surface antibody and a protein marker

Multivalent Antigen

Antigens with multiple epitomes, leading to increased B-cell activation

Parts of an Antibody (there are 5)

• Heavy Chain

• Light Chain

• Hinge Region

• Fab Fragments

• Fc Fragment

Fc Region on antibody

The tail end of an antibody that can bind to cell surface receptors and complement proteins

Fab Regions on antibodies

The site where it binds and Antigen

Polyvalent Antigens

Multiple Identical Epitomes on one antigen

Do antibodies have to match the antigen perfectly?

Nah

Affinity Constant

How favorable it is for the Antibody to bond noncovalently with the Antigen

IgG Antibodies

Primary blood-borne antibodies, also cross placenta

IgM Antibodies

Present on B-Cell membranes, meditates initial immune response, activates bacteria-killers

What do light chains and heavy chains both have? (3 answers)

A constant region, a variable region, and a hypervariable region within the variable region

Precipitin Test

A test to see if an antibody is binding an antigen by looking for a precipitate between two agar wells containing one of each

Immuno-Assays

An unknown antigen is exposed to a primary antibody to a known antigen and a marked secondary antibody to see if they aggregate

Monoclonal Antibodies

Lab-made antibodies that can be used to fight pathogens, cancer, or autoimmune disease

Fluorescence Activated Cell Sorter (FACS)

• Different Abs labelled with different fluorescent markers

• Separated by wavelength

• Can be weighed to identify relative proportion

Is the instructive theory or the selective theory most accurate?

The selective theory

Instructive theory of Antibody Diversity

Ab proteins refold themselves to match an antigen

Selective theory of Antibody Diversity

B-Cells just spam different Ab combos until they find one that is effective

Virgin B-Cells

B-Cells that produce an antibody that hasn’t yet experienced an antigen (no indication of whether or not the ab is effective)

Bence-Jones Proteins

In multiple myeloma, B-Cells become cancerous and create a ton of the same antibody

Nossal-Lederberg Experiment

Showed that a B-cell exposed to two antigens would produce antibodies to one or the other, but not both (evidence for monospecificity)

Primary ab response to an antigen

Slow rise in Abs (mainly IgM)

Secondary ab response to an antigen

More rapid and greater Ab response (mainly IgG)

How is Ab diversity generated?

Recombination of light chain and heavy chain (alternative splicing)

How many Ab combinations are there?

~10¹²

Somatic Hypermutation

Heavy and Light chains undergo a mutation rate that is one million times greater than average

Allelic Exclusion

B-Cells are monospecific, so only one allele will end up being expressed

What are the secondary Ab classes?

IgG, IgE, IgA

Switching from membrane-bound IgM to secreted Ab

As Virgin B-Cells mature, they start secreting antibodies instead of making membrane-bound ones