Immunity and Infectious Diseases

• The primary organs of the immune system are the bone marrow and the thymus
• Hematopoietic cells are classified into myeloid, lymphoid, and Erythroid cells
• Plasma is the liquid component of blood, containing clotting factors made up of hematopoietic cells bound up in a web of protein
• Antibodies are a major protein found in the blood on mucosal surfaces that mediates immune system function
• Antigens are substances that an individual animal sees as foreign or non self and mount an immune response
• The lymphatic system is a network of vessels and nodes that circulate lymph (plasma-derived fluid throughout the body) via the lymph nodes
• Effector cells mediate the immunologic reactions that lead to the killing and elimination of harmful microbes or other harmful substances
• B lymphocytes are central to the immune system. They produce antibodies when activated in an immunologically specific fashion by an antigen
• T lymphocytes recognize antigens in an immunologically specific manner
• Antigen Presenting Cells (APC) are cells that produce small peptides produced by proteases and displays an antigen bound by a major histocompatibility complex (MHC)
• phagocytosis is a clearance mechanism that kills and removes pathogens found in sterile tissues. The ingested microbe is held within a sub cellular organelle called the phagosome
• Natural Killer cells are a type of lymphocyte with cytotoxic activity whose primary function is to patrol the body looking for aberrant cells that have reduced or eliminated expression of MHC-class 1. Their default program is the kill target cells they encounter
• Cytokines are small proteins that are produced by one cell and have a biological effect on another cell or an effect on the producing cell itself. They can result in stimulation, suppression, and/or modification of the immune response
• Viruses have an RNA or DNA genome that can replicate, but they rely on a host cell for their metabolism. They enter the cell by attaching to receptors, replicate, and leave the cell to infect others. Most viruses have been controlled by vaccines.
• A special category of viruses causes disease only with immune deficiency, so-called opportunistic infection
• Bacteria are single, free-living prokaryotic cells, of few of which can parasitize humans and cause disease. Their genome consists of a single loop of DNA. Most cells are contained within a membrane and a more rigid cell wall unless they are "atypical" and are parasitic. Most bacteria can be controlled with antibiotics
• Gram-positive bacteria have a thick sugar amino acid polymer outside a single cell membrane that causes an immune response. Gram-negative bacteria have a thinner peptidoglycan later between two cell membranes and they create less of an immune response. The Mycobacterium is a waxy outer layer that resists the gram stain and a sufficient immune response
• Bacterial variation is a mechanism bacteria use to stay ahead of the environment. This could be done by plasmid transfer, DNA mutations, lateral gene transfer, etc.