Lecture 6 (Part2)

Lymphatic System and Immune System

Lymphatic system

Recovers lost fluid and proteins from capillaries and returns them to circulation

Lymph

Fluid collected by lymphatic vessels and returned to the bloodstream

Lymph nodes

Sites where white blood cells multiply; swell during infection

Spleen

Filters old red blood cells and participates in immune responses

Thymus

Site where T cells mature

Appendix

Acts as a lymphatic organ; inflammation leads to appendicitis

Lacteals

Lymphatic vessels in intestinal villi that absorb fats

First line of defense

Physical and chemical barriers like skin and mucus that block pathogen entry

Second line of defense

Non-specific internal defenses that fight pathogens

Third line of defense

Specific immune response targeting particular pathogens

Innate immunity

Fast, non-specific defense against pathogens

Adaptive immunity

Slower, specific defense targeting particular antigens

Innate recognition

Detects molecules common to pathogens but not found in host cells

Adaptive recognition

Detects specific antigens using specialized receptors

Exoskeleton

Outer protective barrier in invertebrates

Chitin

Structural barrier in invertebrate digestive tracts

Lysozyme

Enzyme that breaks down bacterial cell walls

Recognition proteins

Bind to pathogens and trigger immune responses

Hemocytes

Phagocytic cells in invertebrates that engulf pathogens

Barrier defenses

Physical and chemical barriers preventing pathogen entry

Mucus membrane

Secretes mucus to trap pathogens

Acidic stomach

Low pH destroys ingested pathogens

Acidic skin

Slightly acidic surface inhibits microbial growth

Phagocytes

Cells that engulf and destroy pathogens

Neutrophils

Most abundant phagocytes that rapidly respond to infection

Macrophages

Large phagocytes that engulf pathogens and release signaling molecules

Monocytes

Circulating cells that develop into macrophages

Eosinophils

White blood cells that attack parasites

Basophils

Release histamine during allergic reactions

Mast cells

Release histamine and contribute to inflammation

Dendritic cells

Activate adaptive immunity by presenting antigens

Natural killer cells

Kill infected or cancer cells by releasing toxic substances

Chemokines

Signals that attract immune cells to infection sites

Pyrogen

Substance that causes fever by raising body temperature

Inflammatory response

Response to injury causing redness, swelling, pain, and heat

Rubor

Redness due to increased blood flow

Tumor

Swelling due to fluid accumulation

Dolor

Pain caused by inflammation

Calor

Heat or fever that inhibits pathogen growth

Interferon

Protein that blocks viral replication and enhances immune response

Complement system

Group of proteins that destroy pathogens by forming pores

Pathogen evasion

Strategies used by pathogens to avoid immune detection

Outer capsule

Protective layer preventing recognition and phagocytosis

Lymphocytes

White blood cells responsible for adaptive immunity

B cells

Produce antibodies and mature in bone marrow

T cells

Attack infected cells or assist other immune cells; mature in thymus

Antigen

Substance that triggers an immune response

Antigen receptor

Protein on lymphocytes that binds specific antigens

Epitope

Specific part of an antigen recognized by receptors

Self-tolerance

Ability to avoid attacking the body’s own cells

Clonal selection

Activation and multiplication of specific lymphocytes

Effector cells

Active immune cells that respond immediately to pathogens

Memory cells

Long-lived cells that enable faster secondary responses

Plasma cells

Effector B cells that produce antibodies

Helper T cells

Activate B cells and cytotoxic T cells

Cytotoxic T cells

Kill infected cells by inducing apoptosis

Major histocompatibility complex (MHC)

Molecules that present antigen fragments on cell surfaces

Antigen presentation

Display of antigen fragments on MHC for T cell recognition

Immunological memory

Faster response to previously encountered antigens

Primary immune response

First exposure; slower and weaker response

Secondary immune response

Faster and stronger due to memory cells

Humoral immune response

Antibody-mediated defense in body fluids

Cell-mediated immune response

T cells destroy infected cells directly

Antibodies

Proteins that bind antigens to neutralize or mark them

Immunoglobulins

Another term for antibodies

Neutralization

Antibodies block pathogens from infecting cells

Agglutination

Antibodies clump pathogens together

Precipitation

Antibodies cause soluble antigens to become insoluble

Opsonization

Antibodies mark pathogens for destruction by phagocytes

Complement fixation

Activation of complement proteins to destroy pathogens

Apoptosis

Programmed cell death of infected cells

IgM

First antibody produced; important in primary response

IgG

Most abundant antibody; important in secondary response and crosses placenta

IgA

Found in secretions like saliva, tears, and breast milk

IgD

Involved in B cell development

IgE

Triggers allergic responses

Erythroblastosis fetalis

Condition where maternal antibodies destroy fetal red blood cells