Lecture 1: Functions of the Immune System Flashcards
Classification of microorgansims (smallest to largest): Fungi, Helminths, Viruses, Protozonans, and Viruses
Viruses (obligate intracelular protein), Bacteria (prokaryotic), Fungi (euk: unicellular), Protozoans (euk; unicellular), Helminths (euk: multicellular)
Commensals (Normal flora)
microbes that co-exist with humans WITHOUT causing disease
Pathogens
- Microbes capable of causing human disease
- whether or not they cause disease if 100% dependent on their interation with the immune system
Colonization
The establishment of proliferating microbes ON the skin or mucous membranes
Infection
- The proliferation of microbes IN tissues with the concomitant induction of the immune system
- Progression from colonization to infection to disease depends on host cell immune system
Disease
-The proliferation of microbes in tissues, immune response and resulting DAMAGE and/or impairment of bodily functions
Functions of the Immune System
- Provide surveillance and defense against foreign substances (lymphatic system)
- Help maintain fluid balance: collection of interstitial fluid and return to circulating system –> filtration out microbes
How do we respond to microbial threat?
- Barriers
- physical barriers: ex: skin
- chemical
- biological - Innate immunity: innate once past barrier
- Non-specific mechanisms: directed towards large groups of microbes
- 0-96 hours
- phagocytosis, inflammation, NK cell killing, Complement (alternate pathway), cytokine release - Adaptive Immunity
- specific
- >96hours
- Humoral: B cells and antibodies
- Cell mediated: T-cells and cytokines
Defense mechanisms of the skin
- outer layer: keratinocytes (continually sloughed off)
- when microbes adhere to these cells, they’re not always able to bind and proliferate b/c they’re removed with sloughing off - several water-resistant layers
- no water = not hospital environment for microbes to grow - hair follicles, glands, synthesis of chemical barriers (alpha defensins, beta defensins, DNAses, RNAses etc.) that will impede/destroy microbes
- pH: neutral pH is 7. Skin is 5.5, which is not hospital for the growth of bacterial
Four characteristics of Innate Immunity
- The action is immediate
- Response is non specific
- Broad general classes against bacteria/viruses
- Structural features that microbes have that eukaryotes dont have - Response is not enhanced on repeated exposure to pathogen
- Same level of response the first time we see a microbe is the same level of response we see the 5th/10th/100th time we see it - Generates mediators required to activate the adaptive immune response
- without many cells of the innate immune system, the adaptive immune system won’t be able to function
Cell lineage
- All cells of the immune system in general arise from a singular group of hematopoietic stem cells
- Hematopoietic stem cells –> Myeloid lineage OR Lymphoid lineage
- Lymphoid lineage: Generate natural killer cells, T lymphocytes, and B lymphocytes, and NK cells
- Myeloid lineage: granulocytic cells and the monocytic cells
Cells that are adaptive immunity
T-cells and B cells
Cells that are innate immunity
Eoisinophils, basophils,neutrophils, monocytes/macrophages, endritic cells, NK cells
Granulocytes
- Myeloid lineage
- contain granules in their cytoplasm
- Include eosinophils, basophils, neutrophils
- release granular contents which destroy microbes
Monocytic myeloid cells
- monocytes are immature macrophages
- found in blood, migrates to tissue, and differentiates to become a macrophage
- ***important in bridging gap between innate and adaptive
- main function: phagocytosis
- scavenge looking for microbes/cellular debris/dead/dying cells –> engulf and remove them
- when a macrophage engulfs a microbe, it gets activated and then begins to produce cytokines (chemical messengers secreted by one cell type that can act on another cell type).
