Innate and Adaptive Immunity Overview

Innate Immunity

• Innate immunity is the body's first line of defense against pathogens.
• Physical barriers like skin and mucous membranes prevent pathogens from entering the body.
• Complement system is a group of proteins that work together to lyse pathogens, opsonize them for phagocytosis, and recruit immune cells.
• Phagocytes like neutrophils, macrophages, and dendritic cells engulf and destroy pathogens.
• Memory B cells are a component of adaptive immunity, not innate immunity.

Adaptive Immunity

• Adaptive immunity provides a more specific and targeted response to pathogens.
• Specificity means that each immune response targets a specific antigen.
• Memory allows the immune system to mount a faster and more effective response upon re-exposure to the same antigen.
• Diversity allows for a wide range of responses to different antigens.
• Immediate response is a characteristic of innate immunity, not adaptive immunity.

T Cell Education

• Thymic education is the process by which T cells learn to distinguish self from non-self antigens in the thymus.

Antigen Presentation

• Major Histocompatibility Complex (MHC) II molecules present antigens to CD4+ T cells.
• MHC I molecules present antigens to CD8+ T cells.

Immune Cell Functions

• B lymphocytes are responsible for antibody production.
• T helper cells activate and regulate other immune cells.
• Cytotoxic T cells directly kill infected or abnormal cells by releasing cytotoxic substances.
• Neutrophils are involved in phagocytosis of pathogens.
• Dendritic cells are professional antigen-presenting cells that activate naive T cells.
• Macrophages are phagocytic cells that engulf and destroy pathogens, present antigens, and secrete cytokines.

Immune Responses

• Clonal selection is the process by which lymphocytes capable of responding to a specific antigen proliferate and differentiate into effector cells.
• Immunological memory is the ability of the immune system to respond more quickly and effectively to a pathogen it has encountered before.
• Interferons are cytokines that are produced by cells in response to viral infections.
• Lymphatic system is responsible for transporting lymph, filtering pathogens, and maturation of lymphocytes.

Vaccination

• Recombinant vaccines are made by inserting the gene for a pathogen's antigen into another organism.
• Vaccines help to stimulate the adaptive immune system and develop immunity against specific pathogens.

Antibodies

• IgM antibodies are the first type of antibody produced in a primary immune response and are restricted to the circulation.
• IgA antibodies are found in secretions and provide mucosal immunity.
• IgG antibodies are the most abundant in serum and can cross the placenta.

Immune Processes

• Diapedesis is the movement of white blood cells through blood vessel walls.
• Somatic hypermutation is a process that increases the diversity of antibody responses.
• Isotype switching is the process by which B cells switch from producing one type of antibody isotype to another.

Hypersensitivity Reactions

• Hypersensitivity reactions are exaggerated immune responses to antigens.

Autoimmune Diseases

• Autoimmune diseases occur when the immune system attacks the body's own tissues.

Cytokines

• Cytokines are signaling molecules that regulate immune responses and mediate inflammation.

Immune Cells and Processes (Continued)

• Eosinophils are involved in defense against parasitic infections.
• Natural killer (NK) cells kill virus-infected and tumor cells.
• Follicular dendritic cells retain and present antigens to B cells.
• NETosis is the process by which neutrophils release DNA and proteins to form extracellular traps (NETs) to trap pathogens.

Lymphatic System and Tissues

• Spleen filters blood-borne pathogens and stores platelets.
• Thymus is the site of T cell maturation.

Immune Tolerance

• Immunological tolerance is the ability of the immune system to avoid reacting to self-antigens.
• Regulatory T cells suppress immune responses and help maintain tolerance to self-antigens.

Antigen Processing

• Antigen processing is the breakdown of antigens into peptides.

Immune System Responses

• Acute phase response is a rapid and innate immune response characterized by fever, increased vascular permeability, and production of acute phase proteins.
• Invariant natural killer T (iNKT) cells are a type of T cell that recognize lipid antigens.