Immunity Flashcards

Immunity: Innate and Adaptive

Immunity, or resistance, is the body's ability to protect against diseases from microorganisms and their products.
Lack of immunity is called susceptibility.
The immune system prevents pathogen entry or seeks and eliminates them if they enter.
Innate and adaptive immune systems work together but differ in their mechanisms.

Adaptive immunity is highly specific and acquired through exposure to pathogens.
It activates to fight specific pathogens by recognizing and destroying them.
Response is delayed, with a lag time between exposure and maximal response.
Demonstrates memory: subsequent exposures lead to quicker and stronger responses.

The innate immune system prevents entry and initial spread of microorganisms.
It responds within seconds or minutes of pathogen entry, regardless of prior exposure.
This system includes both a first and second line of defense.

Describe the innate immune response, including surface and internal defenses.
Explain the role of skin, mucus, stomach acid, phagocytes, white blood cells, antimicrobial peptides, and inflammation in innate immunity.
Explain adaptive immunity.
Explain antigens and their role in pathogen elimination.
Describe antibody structure and function.
Know the functions of B and T lymphocytes (cytotoxic, helper, and regulatory) in adaptive immunity.
Understand the key characteristics of cell-mediated immune response: diversity, specificity, memory, and self/non-self-distinction.
Describe active and passive immunity, with natural and artificial examples.
Describe Edward Jenner's contribution to immunology.
Explain the immune system's role in allergies and autoimmune diseases.

Humans are constantly exposed to microorganisms, some of which are pathogenic.
Host defense mechanisms, or the immune system, prevent pathogens from causing damage.
Two types of immune defense systems: innate (nonspecific) and adaptive (specific) immunity.
These systems involve multiple types of cells and molecules and work together.

The immune system initially prevents pathogen entry via surface defenses.
These defenses are grouped into structural, mechanical, and biochemical categories.

Skin blocks entry of most microorganisms.
- It is a strong physical barrier that is almost impossible for microorganisms to penetrate when intact.
- The epidermis is composed of tightly packed epithelial cells containing keratin, a protective protein.
- The top layer of cells is dead and constantly shed, removing colonizing microbes.
- The dryness of the skin also inhibits bacterial growth.
Microorganisms can enter through broken skin (injury or burn), leading to subcutaneous infection.
Mucous membranes line body cavities (gastrointestinal, respiratory, and genitourinary tracts).
- They block entry and remove microbes from the surface.
- Mucous membranes contain tightly packed cells that block microorganisms from entering the body.
- They secrete mucus, a viscous glycoprotein substance that traps microbes, dust, and dirt.
- Respiratory tract mucus membranes have cilia, which sweep mucus containing trapped microbes upward toward the throat.
- Patients on ventilators are susceptible to upper respiratory infections due to inhibited ciliary motion.
- Mucus that traps microbes in the gastrointestinal tract is removed via defecation or vomiting.

Mucus traps or washes away microbes.
Tears wash away microorganisms in the eyes.
Earwax blocks microorganism entry into the ears.
Saliva washes microorganisms from the mouth and teeth surfaces and inhibits microbial growth via acidic pH.

Enzymes and acids destroy pathogens.
Skin and mucous membranes secrete chemical factors to prevent colonization.
Lysozyme is found in sweat, tears, saliva, nasal secretions, and urine, killing gram-positive bacteria by breaking down their cell walls.
Skin secretions are acidic, inhibiting microbial growth.
Stomach acid maintains a low pH (~2.0) to kill most microorganisms.
Sebaceous glands secrete acids that block bacterial growth.
The vagina allows growth of Lactobacillus acidophilus, which produces lactic acid, maintaining a low pH that inhibits the growth of other microbes.

Harmless microorganisms on the skin, in the stomach and intestines, and on mucous membranes block pathogen colonization.
They compete for space, consume available nutrients, alter oxygen and pH levels, and produce harmful substances for pathogens.
The collection of these friendly microbes is called the human microbiota (also called normal flora).

Occurs when pathogens bypass surface defenses.
Entry can occur via wounds, trauma to the skin or mucous membranes, or pathogen-produced substances that allow entry.
The flu virus disrupts mucous membranes in the respiratory tract, enabling entry.
Pathogens find a suitable environment (proper pH and temperature) inside the body and multiply rapidly.
Internal defense, composed of physiological barriers, is activated.
Antimicrobial proteins, phagocytic cells (cells that engulf foreign material), inflammation, and fever participate in this second line of defense.
These steps occur due to white blood cells (leukocytes) in the blood.

Plasma (liquid part of blood).
Thrombocytes (platelets) help with blood clotting.
Erythrocytes (red blood cells) carry oxygen around the body.
Leukocytes (white blood cells) perform immune system functions.
Certain leukocytes are responsible for the second line of defense, while others are responsible for adaptive immunity.
Leukocytes are divided into granulocytes, monocytes, and lymphocytes, each with specific cell types and functions.