Immunology

• The immune system is composed of two main components, the innate immune response (non-specific) and adaptive immunity.
• Innate immunity provides an immediate defense against pathogens through physical barriers such as skin and mucous membranes, chemical defenses like acidic pH and enzymes, and cellular responses including phagocytosis by macrophages and neutrophils.
• Adaptive immunity involves specific recognition of antigens by lymphocytes, leading to clonal expansion and memory cells that can respond quickly upon reexposure to the same antigen.
• Adaptive immunity involves specific recognition of antigens by lymphocytes and memory cells that can respond quickly to subsequent exposure to the same antigen.
• Antibodies are produced by B cells and play a role in both humoral and cell-mediated immunity.
• T cells recognize antigens presented on MHC molecules and have different functions depending on their subtype.
• Antibodies are proteins produced by B cells that bind specifically to foreign substances called antigens.
• Cytotoxic T cells kill infected host cells directly, while helper T cells activate other immune cells and promote antibody production.
• T cells recognize antigens presented on MHC molecules and play roles in both innate and adaptive immunity.
• Cytotoxic T cells kill infected or cancerous cells directly, while helper T cells activate other immune cells and promote antibody production.
• The immune system is composed of two main branches: innate (non-specific) and adaptive (specific).
• Regulatory T cells suppress excessive immune responses and prevent autoimmune diseases.
• Natural killer (NK) cells are part of the innate immune system and kill infected or cancerous cells without prior sensitization.
• Memory cells persist even after an infection is cleared, providing rapid protection against future exposures to the same pathogen.
• Memory T cells provide long-lasting protection against future infections with the same pathogen.
• Both innate and adaptive immunity involve the activation of T cells and antibody production by B cells.
• The complement system is a group of plasma proteins that work together with antibodies to destroy pathogens through various mechanisms such as opsonization, chemotaxis, and membrane attack complex formation.
• The adaptive immune system has two main components: humoral (antibody) immunity and cellular (cell-mediated) immunity.
• Immune response is initiated when antigens from microorganisms or other foreign substances enter the body.
• The immune system is composed of two main branches - the innate immune response (non-specific) and the adaptive immune response (specific).
• Complement activation occurs when C1q recognizes an antigen-antibody complex or when mannan-binding lectin (MBL) recognizes carbohydrates on microbial surfaces.
• Naïve CD4 T cells recognize pathogen peptides presented by MHC class II molecules.
• TH1 (T Helper 1) cells activate type 1 responses and help to eradicate infections by microbes that can survive or replicate within macrophages.
• The main CD4 effector subsets are TH1, TH2, TH17, and TFH, which activate their target cells and Treg (regulatory T cells), which inhibit the extent of immune activation.
• CD4 cells enhance the effector functions of other cells that eradicate pathogens.
• The IL-2 produced by activated CD4 T cells also acts to promote effector CD8 T cell differentiation.
• Primeing is the activation and clonal expansion of a naive T cell on its initial encounter with antigen.
• Naïve CD4 T cells differentiate into distinct pathways that generate effector subsets with different immunological functions.
• CD 40 ligand binds to CD 40 on the dendritic cell, delivering an additional signal that increases the expression of B7 and 4-1BBL by the dendritic cell, which in turn provides additional co-stimulation to the naive CD8 T cell.
• Innate immunity is not sufficient to protect us fully from infectious diseases because many pathogens have features that allow them to evade innate immune responses.
• The antigen-specific responses generated by our powerful adaptive immune system are usually needed to resolve infections successfully.
• Adaptive immunity is initiated when a pathogen overwhelms innate defense mechanisms.
• Types of mechanisms in adaptive immunity include T cell-mediated Immunity and Humoral Immune Response.
• T cell-mediated Immunity involves T cells that enter the bloodstream after competing primary development in the thymus, leave the blood to migrate through the lymphoid tissues, and return to the bloodstream via the lymphatics.
• Naïve T cells are mature recirculating T cells that have not yet encountered their specific antigens and must meet its specific antigen to participate in an adaptive immune response.
• The antigen is presented to naïve T cells as a peptide: MHC complex on the surface of an antigen-presenting cell.
• Activation of naïve T cells requires T cell receptor (TCR) – peptide – MHC interaction (signal 1) and co-stimulation (signal 2) for full activation.
• Co-stimulation can be provided by so-called professional antigen-presenting cells (APCs; i.e. dendritic cells, macrophages and B cells).
• In the absence of co-stimulation, the T cells will become anergic.
• Antigen presenting cells are distributed by type in specific areas of the lymph node.