Immunology and Endocrinology Notes

Practice Final Exam

• Practice final exam uploaded; cumulative, with the first 30 questions covering major topics.

Immune System

• Keeps us healthy by protecting us from pathogens like bacteria and viruses.
• It also protects us from our own mutated cells like cancer cells.
• An antigen is anything that the body perceives as a threat and provokes an immune response.
• The immune system immobilizes, incapacitates, and destroys antigens.
• A secondary response to antigens is an inflammatory response, which has predictable patterns.
• Inflammation involves white blood cells engulfing antigens/pathogens at the site of attack.
• Cardinal signs of inflammation result from antigens invading the breached first barrier (skin).
• White blood cells dilate vessels to enter the area, engulfing pathogens.
• Water follows, leading to heat and swelling; the body may induce a fever to create an inhospitable environment for the attacker.
• When a normal circulating white blood cell encounters a pathogen, it engulfs it as part of the nonspecific defenses. The presentation of a specific antigen mark leads to the adapted or acquired immune system response.

Analogy for Immune System: Military

• Local problem: Call the police or public safety. Nonspecific Immune System
• Alien invasion: Need bigger guns like the Navy (B lymphocytes) and Army/Marines (T lymphocytes).

Nonspecific vs. Acquired Immune System

• Nonspecific: General response (red, hot, swollen, fever).
• Acquired: Specific response triggered if the problem is severe enough and in body fluids (blood).

B Lymphocytes (Navy)

• Produce antibodies that circulate in the blood to intercept pathogens.
• Think B cells -> B for blood -> fluid immunity.
• Humoral division.
• Antibodies act like submarines, sinking the alien ship (pathogen) before it reaches landfall (infection).

T Lymphocytes (Army/Marines)

• Deal with problems that have already made it to land (infection).
• Viruses hijack DNA inside cells; cancer involves mutated DNA—intracellular problems.
• T cells kick open doors and "kick some asses" inside tissues.
• Think T cells -> tissues.
• Mature in the thymus.

How the Navy (B Cells) Works

• Exposed to an antigen after a normal white blood cell (local police) picks up a pathogen.
• The white blood cell eats the pathogen and takes the mark it was carrying.
• A virus or bacteria is made of proteins, which have specific codes.
• The immune system recognizes a protein on the virus as foreign and bears its mark.
• The bone marrow makes all blood cells. B cells differentiate into:
  • Plasma cells: produce antibodies
  • Memory B cells
• T cells go to the thymus for boot camp.

Analogy for Immune System: Government

• Helper T Cells (CD4 T Cells): most important. Analogy to the President, or Secretary of Defense
• T helper cells govern both the B cell navy and the T cell army.
• Other cells present antigens to the T helper cell, which then develops a bunch of T helper cells that look for the antigen.

Cytotoxic T Cells

• The army or marines that go into tissues, looking for cellular problems.
• Activated once there's a specific response.
• They destroy infected cells that have made it into the land, the tissues.
• They can look inside cells and see if the nucleus is being hijacked.

T Suppressor Cells

• These cells suppress the immune response.
• They tell the president (T helper cell) to turn down the immune response after the enemy is beaten.
• Prevents an overly exaggerated immune response that could damage the body's own tissues.
• Over exaggerated immune responses can cause autoimmune conditions.

How Navy (B Cells) Works

• B cells are responsible for the humoral division, operating in Blood; lymphatic system, saliva, and tears employ antibodies.
• The president (T helper cell) directs production of specific antibodies tailored to different antigen shapes to prevent pathogens from attaching to cells.

Memory Cells

• The first exposure generates a certain level of antibodies.
• The second exposure leads to a much stronger response, producing more antibodies and memory cells.
• Repeated exposure increases immunity over time.

Putting it All Together

• An antigen must first get through the innate defenses (skin, etc.).

• The innate immune system:

  • Skin lining of stratified squamous cells: several thin layers for protection.
  • Cuts allow easier infection by bacteria or viruses.
  • Colds, swollen lymph nodes, and fever.

• A nonspecific cell eats the pathogen then presents to a naive T helper cell.

• The T helper cell (president) becomes activated and says, "look for that antigen."

• The T helper cell develops a memory cell for a stronger response the next time.

• The T helper cell then talks to the Navy (B cells) to make antibodies.

• The T helper cell also talks to the T side (cellular side, tissue side) to activate cytotoxic T cells which are the army.

• All of these cells are specific for that specific pathogen.

• The T helper cell can also activate other nonspecific defenses.

• Multiple white blood cells are activated, with neutrophils (70% of blood) being the first responders.

• After eating pathogen, nonspecific cell presents to either activate B side (Navy) or T helper cell. B cells can also be directly activated.

• Stimulating B cells alone only creates antibodies; involving the T helper cell creates antibodies plus activates the army too.

• Most white blood cells eat pathogens (stranger danger), but T cells-lymphocytes trigger a specific response.

• B and T cells are lymphocytes, which are a type of white blood cell.

Mechanisms

• B cells for blood, producing antibodies; T cells for tissues.

Endocrine System

• System of glands that produce and secrete chemical messengers with broad effects throughout the body.

Endocrine vs. Exocrine Glands

• Endocrine: Gland that releases a chemical message (hormone) into the circulatory system, acting on specific cells sensitive to that message. More widespread
• Exocrine: Gland that has a duct that goes into a specific location (e.g., parotid gland producing saliva into the mouth via ducts).

How Endocrine Gland Works (e.g., Pituitary Gland, Pancreas)

• Specialized cells release a hormone (e.g., growth hormone, insulin) into the blood.
• The hormone travels to cells that can listen to its message (have the appropriate receptors).
• Pancreas produces insulin that goes into the blood, lowering blood glucose levels by instructing to take up glucose.
• The pituitary produces growth hormone that will tell certain cells to grow.

Endocrine vs. Nervous System

• The endocrine system is slower but more sustained than the nervous system.
• The nervous system relies on neurotransmitters; is very fast via action potentials using electrolytes.

Hormone Action

• A hormone is released and goes into circulation.
• It will only fit certain receptors due to its specific shape (amino acids, hydrogen bonds, etc.).
• Insulin resistance occurs when the cell shape is altered, preventing insulin from binding effectively and affecting response. Because the protein is folded and will not work as effectively. Can be due to different hydrogen bonds along the molecule causing a folding issue and therefore reducing its ability to fit a receptor.
• Only cells with the matching receptor will be able to respond to a specific hormone.

Hypothalamus

• Regulates the pituitary gland, which has two parts: anterior and posterior.

Posterior Pituitary

• Derived from neural tissue (axons); appears white under a microscope.
• Releases ADH and oxytocin, but these are actually made in the hypothalamus and transported to the posterior pituitary for release.
• Considered an icicle of the brain—an extension of the brain.

Anterior Pituitary

• More vascular; produces its own hormones.
• The hypothalamus tells the anterior pituitary to release hormones.

Oxytocin

• Involved in positive feedback loops such as childbirth when the baby's head presses on the cervix, leading to uterine contractions and the expulsion of the baby.
• Amplifying effect, rather than shutting it off (negative feedback).
• Also involved in the ejection of milk during breastfeeding.

Anterior Pituitary Hormones

• Thyroid Stimulating Hormone (TSH): Communicates with the thyroid gland, which regulates metabolism.
• Metabolism: C6H{12}O6 + O2 \rightarrow CO2 + H2O + ATP + Heat
• Thyroxin is produced to increase cells' ability to do cellular respiration, burning calories.
  • Hyperactive thyroid leads to burning calories and feeling hot. You will do this formula more so you're burning more calories.
  • Underactive thyroid leads to feeling cold with an eating the same amount of foods so not burning fuel. The glucose therefore can be stored.
• Adrenocorticotropic hormone (ACTH): this goes to: goes to adrenal glands for dealing with stress.
  • Cortisol increases heart rate, blood glucose levels, and blood pressure under stress. It increase glucose levels so there's fuel to run from a tiger.
• Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH): hormones are for the reproductive system.
• Prolactin: Hormone production of milk.
• Growth Hormone: Promotes muscle growth (by building proteins) and bone density and causes the muscles to grow by lifting heavy weight and putting them under stress. It creates more glucose because muscles needs to draw energy. Prevents the liver from storing sugar overnight to ensure glucose is available for the brain. Calcium, CA, calcitonin lowers blood calcium.