1.1 - ANAPHY & IMMUNE RESPONSE

immunity

• the body's ability to recognize and respond to foreign substances (antigens such as microorganisms, toxins, allergens, or abnormal cells) in order to protect itself.

• Defense

• Homeostasis

• Surveillance

Functions of Immunity

Defense

Attacks and eliminates bacteria, viruses, fungi, and parasites before they cause infection.

Homeostasis

Clears out damaged or dead cells so tissue stays balanced and can repair itself.

Surveillance

Continuously checks for abnormal cells (early cancer cells) and destroys them.

• Self/Non-self Recognition

• Memory

• Antibody Production

• Self-Regulation

Characteristics of Immunity

Self/Non-self recognition

Ignores the body's own cells; reacts only to foreign antigens.

Memory

Responds faster and stronger on re-exposure — the principle behind vaccination.

Antibody Production

Makes antibodies tailored to specific antigens for a precise, targeted response.

Self-regulation

Activates against a threat and then deactivates once it is cleared, preventing overreactions such as allergies or autoimmune disease.

• skin

• mucous membrane

• GI tract

• respiratory tract

barriers to infection

skin

• tightly packed, constantly shedding cells plus antimicrobial sweat and sebum block most microbes

• broken by cuts, bites, burns, or IV lines.

mucous membrane

• line the respiratory, GI, urinary, and reproductive tracts

• antimicrobial secretions (e.g., lysozyme in tears) trap and destroy microbes.

respiratory tract

• cilia sweep mucus and trapped particles upward (the mucociliary escalator)

• coughing expels irritants

• alveolar macrophages engulf whatever gets through.

gi tract

• stomach acid and enzymes destroy ingested microbes

• peristalsis and cell shedding physically clear them

• normal gut flora crowds out pathogens.

lysozyme

what’s the enzyme in tears?

mucocilliary elevator

cilia sweep mucus and trapped particles upward… what is it called?

achlorhyria

condition where mababa ang stomach acid

Clostridioides difficile

agent that causes colitis

• bone marrow

• thymus

primary lymphoid organs

primary lymphoid organs

• where the immune cells are made and mature

Bone Marrow

• Birthplace of all blood cells 

• B cells mature here

Thymus

T cells mature here and learn to recognize antigens

• spleen

• lymph notes tonsils

secondary lymphoid organs

secondary lymphoid organs

where they encounter and respond to antigens

Spleen

• Filters blood, removes old red blood cells and microbes, stores platelets.

Tonsils

• Guard the throat/mouth entryway against inhaled or ingested pathogens

Lymph Nodes

• Filter lymph fluid and trap pathogens; swelling signals an active immune response

mononuclear phagocytes

• capture, process, and present antigens to lymphocytes

• perform phagocytosis (engulf and digest pathogens)

• include monocytes (in the bloodstream) and macrophages (in tissues such as the lungs, liver, and spleen)

macrophage and monocytes

what are under mononuclear phagocytes?

bloodstream

where to find monocytes?t

tissues (lymph, liver, spleen)

where to find macrphages?

lymphocytes

• originate from lymphoblasts in the bone marrow and are the primary infection-fighting white blood cells

B cells and T cells

Types of Lymphocytes

b lymphocytes

• differentiate into plasma cells that produce antibodies — the basis of humoral immunity

• mature in bone marrow

• make proteins called antibodies that lock onto free bacteria and viruses in blood or lymph.

T-cell

• provide cell-mediated, long-term immunity against intracellular threats

• mature in thymus

• Attack body cells already hijacked by viruses or cancer, and helper * direct other immune cells.

Cytotoxic T Cells (CD8+)

• destroy infected or abnormal cells directly using cytolytic enzymes

Helper T Cells (CD4+)

• coordinate both humoral and cell-mediated responses

• activate B cells, cytotoxic T cells, and macrophages

natural killer cells

• kill virus-infected or tumor cells without needing prior sensitization

Dendritic Cells

• capture antigens at entry points (skin, mucosa) and carry them to T cells

• after capturing an antigen, they migrate to lymphoid tissue and present it to a matching T cell, which is essential for starting the adaptive immune response

Cytokines

• chemical messengers that direct cells to grow, activate, or stand down

Interleukines

• promote the development of T and B lymphocytes (e.g., IL-2 boosts T-cell proliferation)

Colony-stimulating Factors

promote blood cell growth in the bone marrow (e.g., G-CSF stimulates neutrophil production)

Interferons

interferons have antiviral and immune-activating effects (e.g., IFN-alpha is used to treat hepatitis B and C)