Human Immunity How our body s cells defend against microbial and viral invaders
What is Immunity? The word immunity comes from the Latin immunus meaning free of burden. Thus; it is a body s general ability to resist infection or disease. The study of immune responses in the body is referred to as immunology.
Types of Immunity There are two types of immune response: *Nonspecific immune response (known also as nonspecific resistance or innate or natural immunity) *Specific immune response (known also as acquired, adaptive or specific immunity)
Non-specific immune response This type of immunity offers resistance to microbial infection or disease through inheritance. Mechanisms such as skin, the conjunctiva of the eye, mucous membranes, and lysozyme (a special enzyme found in saliva, mucous, tears and human milk that breaks down the peptidoglycans in bacterial cell walls.)
First line of defense The non-specific immune response is your first line of defense against disease and infection. It attacks foreign particles equally and has no immunological memory.
Specific Immune Response Is keyed toward specific foreign agents. Effectiveness is increased over time as the body is repeatedly exposed to the foreign agent. Has an immunologic i memory; substances that are recognized are called antigens. Anti: antibody Gen: generators
Antigens Antigens cause cells to replicate and create specialized proteins that add protection to the cell. B-Cells produce antibodies called glycoprotein. They act by sticking to certain antigens and make them inactive or destroy them completely.
Cooperative Systems The specific and non-specific immune systems; while different; do not act alone. Most of the time they cooperate to increase the effectiveness of the immune system and eliminate pathogens from the body.
Example of how specific and nonspecific systems work together
Cells of the Immune System Leukocytes: (Greek: leukos: white and kytos: cell.) White blood cells. Found within tissues and circulating around the body; work with other leukocytes and identify and destroy the foreign agent.
Types of Leukocytes Monocytes: (Greek monos: one cyte: cell) Produced in bone marrow. Once in the blood stream they circulate, grow, migrate to tissues and mature into macrophages or dendritic cells.
Types of Leukocytes Macrophages (Greek: macros: large phagein: to eat) They come from monocytes; but differ in size and content. Membranes contain specialized receptors that recognize the components of pathogens such as lipopolysaccharides, petidoglycan from bacteria, zymosan from fungal cell walls, viral nucleic acids and foreign DNA.
Types of Leukocytes Granulocytes have irregularly shaped nuclei; sometimes giving them the name polymorphonuclear leukocytes. The cytoplasm of these cells contains special granules that contain substances that kill microorganisms and impact the inflammatory response. There are 3 types of granulocytes.
Types of Granulocytes Basophils: (Greek: basis: base and Philein: to love) Non-phagocytic Work by releasing compounds of histamine, prostaglandins, serotonin and leukotrienes. Influence the tone and diameter of blood vessels. Have an affinity for immunoglobulin (associated with allergic reactions)
Types of Granulocytes Eosinophils: (Greek: eos: dawn philien: to love) Migrate from the bloodstream to tissues such as mucous membranes. Release specialized molecules that damage parasitic plasma membranes. Increased during allergic reactions.
Types of Granulocytes Neutorphils: (Greek: neuter: neither, philien: loving) Contain specialized granules called primary and secondary granules. Primary granules contain peroxidase, lysozyme, defensins and other enzymes Secondary granules contain collagenase, lactoferrin, catheicidins and lysozyme. y The compounds contained in both of the granule types work to digest foreign material after it has been phagocytosed Create antimicrobial compounds that kill ingested microbes. Part of the body s inflammatory response as well.
Mast Cells Come from bone marrow Differentiate in blood and connective tissue. Similar to basophils in active substances; but arise from putative mast cell precursors and not from myeloblasts as basophils do. Play an important role in the development of allergies and hypersensitivities.
Dendritic Cells Found in skin and mucous membranes of the nose, lungs and intestines. Encounter pathogens and engulf them in the process of phagocytosis. Once processed; they are presented to T-cells.
Specific Immune System Lymphocytes: (Latin: lympha: water cyte: cell) The major cells of the specific immune system Three different types Born in bone marrow; travel as inactive, non-replicating cells.
Types of Lymphocytes T-Cells Mature in the thymus gland Can remain in thymus, circulate in blood or stay in lymph nodes and spleen. Require a specific antigen to bind to their receptors. Produce cytokines which stimulate cells to mature and differentiate, produce new products or cause others to die.
Types of Lymphocytes Natural Killer Cells: (NK cells) Large, non-phagocytic, granular lymphocyte Destroys malignant cells and cells infected with microorganisms. Bind to antibodies that coat infected cells and causes cellular death through antibody dependent cell mediated cytotoxicity. Specialized proteins are recognized on the surface of the host cells; releases a special protein and cytotoxic enzymes that causes the cell to form pores and lyse.
Types of Lymphocytes B-Cells Reach maturity in the bone marrow. Travel to lymphoid organs and become activated; are now called plasma cells. Secretes large amounts of glycoproteins called antibodies that can directly neutralize toxins and viruses. Stimulates phagocytic response in other cells.
Cells of the Immune System: