1. What is innate immunity?
Innate immunity is the body’s built-in, first-line defense system that is
present from birth.
It’s nonspecific — meaning it reacts to any invader, not just a specific
pathogen — and responds within minutes to hours.
It includes:
• Physical barriers (skin, mucous membranes)
• Chemical barriers (stomach acid, lysozyme in tears/saliva)
• Cellular defenses (phagocytes, natural killer cells)
• Inflammatory response (swelling, redness, heat, pain)
Innate immunity does not have memory — it reacts the same way
each time to a repeated threat.
2. How does the skin act as a physical barrier?
The skin works like a fortress wall — its epidermis is made of tightly
packed cells filled with keratin, which is waterproof and resistant to
pathogen entry.
It also:
• Produces sebum (oily secretion) with antimicrobial properties
• Has a slightly acidic pH (~5.5) that inhibits bacterial growth
• Constantly sheds dead skin cells, physically removing microbes
3. What cells are involved in innate immunity?
Key innate immune cells:
• Neutrophils – Fast-acting phagocytes, arrive first to infection site
• Macrophages – Large phagocytes, engulf pathogens, present
antigens to adaptive immune cells
• Dendritic cells – Antigen-presenting cells, bridge innate and
adaptive immunity
, • Natural killer (NK) cells – Destroy virus-infected and cancerous
cells without prior exposure
• Basophils & Mast cells – Release histamine and inflammatory
mediators
• Eosinophils – Defend against parasites, help modulate allergic
reactions
4. Describe each type of leukocyte and explain their function:
• Neutrophils: Main infection responders; engulf and destroy
bacteria/fungi
• Eosinophils: Fight parasitic worms; involved in allergies/asthma
• Basophils: Circulating cells releasing histamine in allergic reactions
• Monocytes: Circulate in blood; differentiate into macrophages or
dendritic cells in tissues
• Lymphocytes: Include B cells (antibody production), T cells (cell-
mediated immunity), and NK cells (nonspecific killing of
abnormal cells)
5. Describe adaptive immunity:
Adaptive immunity is specific — it tailors its response to a particular
pathogen.
It has memory, so the second exposure to the same pathogen is faster and
stronger.
Two branches:
• Humoral immunity – B cells producing antibodies
• Cellular immunity – T cells directly killing infected cells or
coordinating immune responses
6. What are antigens?
Innate immunity is the body’s built-in, first-line defense system that is
present from birth.
It’s nonspecific — meaning it reacts to any invader, not just a specific
pathogen — and responds within minutes to hours.
It includes:
• Physical barriers (skin, mucous membranes)
• Chemical barriers (stomach acid, lysozyme in tears/saliva)
• Cellular defenses (phagocytes, natural killer cells)
• Inflammatory response (swelling, redness, heat, pain)
Innate immunity does not have memory — it reacts the same way
each time to a repeated threat.
2. How does the skin act as a physical barrier?
The skin works like a fortress wall — its epidermis is made of tightly
packed cells filled with keratin, which is waterproof and resistant to
pathogen entry.
It also:
• Produces sebum (oily secretion) with antimicrobial properties
• Has a slightly acidic pH (~5.5) that inhibits bacterial growth
• Constantly sheds dead skin cells, physically removing microbes
3. What cells are involved in innate immunity?
Key innate immune cells:
• Neutrophils – Fast-acting phagocytes, arrive first to infection site
• Macrophages – Large phagocytes, engulf pathogens, present
antigens to adaptive immune cells
• Dendritic cells – Antigen-presenting cells, bridge innate and
adaptive immunity
, • Natural killer (NK) cells – Destroy virus-infected and cancerous
cells without prior exposure
• Basophils & Mast cells – Release histamine and inflammatory
mediators
• Eosinophils – Defend against parasites, help modulate allergic
reactions
4. Describe each type of leukocyte and explain their function:
• Neutrophils: Main infection responders; engulf and destroy
bacteria/fungi
• Eosinophils: Fight parasitic worms; involved in allergies/asthma
• Basophils: Circulating cells releasing histamine in allergic reactions
• Monocytes: Circulate in blood; differentiate into macrophages or
dendritic cells in tissues
• Lymphocytes: Include B cells (antibody production), T cells (cell-
mediated immunity), and NK cells (nonspecific killing of
abnormal cells)
5. Describe adaptive immunity:
Adaptive immunity is specific — it tailors its response to a particular
pathogen.
It has memory, so the second exposure to the same pathogen is faster and
stronger.
Two branches:
• Humoral immunity – B cells producing antibodies
• Cellular immunity – T cells directly killing infected cells or
coordinating immune responses
6. What are antigens?
