Immunology Lecture Notes PDF

Immune Systems BIOL233W2 Prof HMG Lattorff SU1 | Introduction to the Immune System Lecture 1 | What is Immunology Lecture 2 | Different types of pathogens and diseases caused Lecture 3 | Overview of the Immune System Lecture 4 | Malfunctioning of the Immune System SU1 | Learni...

Immune Systems BIOL233W2 Prof HMG Lattorff SU1 | Introduction to the Immune System Lecture 1 | What is Immunology Lecture 2 | Different types of pathogens and diseases caused Lecture 3 | Overview of the Immune System Lecture 4 | Malfunctioning of the Immune System SU1 | Learning Outcomes Host Direct / indirect life cycle Symbiosis Adaptive immunity Mutualism Innate immunity Commensal microorganism Pathogen transmission Parasite Recognition of self vs non-self Pathogen Antigen Pathogenesis Antigen presenting cells Zoonosis T cells Vector B cells SU1 | host vs pathogen Hosts permanently exposed to wide range of pathogens Pathogens – disease causing organisms (= infectious agents = germs) Probably, pathogens are most frequent organisms on earth as every host is affected by several pathogens SU1 | symbiosis SU1 | regularly associated microorganisms Microbiota Gut Skin Sexual organs (vagina) Range from mutualistic (positive) to commensal (neutral) SU1 | pathogens Negative impact on host Hosts defend themselves using the immune system, pathogens trying to overcome the defence of the host SU1 | four major groups of pathogens Viruses Bacteria Fungi Parasites Protozoan parasites (unicellular) Metazoan parasites (multicellular) SU1 | pathogens - viruses Intracellular pathogens Replicate / multiply through intracellular synthesis of viral components Use host transcription machinery (cannot replicate without a host) Consist of genetic material (either DNA or RNA, single- or double-stranded) and virus capsid (protein) and sometimes and lipid envelope SARS-CoV-2 HPV Influenza A H1N1pdm SU1 | pathogens - viruses SU1 | virus replication (SARS-CoV-2) SU1 | pathogens - bacteria prokaryotes Genetic material free in cytoplasm Ubiquitous, every habitat harbours bacteria SU1 | pathogens - bacteria Bacterial species disease Clostridium tetani tetanus Mycobacterium leprae leprosy Mycobacterium tuberculosis tuberculosis Vibrio cholerae cholera Treponema pallidum syphilis Salmonella sp. Food poisoning Bacillus anthracis anthrax Streptococcus pyogenes Scarlet fever SU1 | pathogens - fungi eukaryotes Genetic material in nucleus 300 fungi pathogenic to humans 2 million deaths per year (more than malaria) SU1 | pathogens - fungi fungal species disease Cryptococcus neoformans cryptococcosis Candida auris multidrug-resistant illness especially in hospitals Candida albicans (opportunistic Candidiasis (mouth, skin, genitals) pathogen) Aspergillus fumigatus Immunodeficient or immunocompromised people, pulmonary infections Aspergillus flavus Produce toxins (aflatoxin), on maize Trichophyton, Epidermophyton, Athlete’s foot (= tinea pedis), Onychomycosis Microsporum (tinea unguium) SU1 | pathogens - parasites eukaryotes Genetic material in nucleus Subdivided into Protozoa (unicellular) Metazoa (multicellular) SU1 | pathogens – parasites - Protozoa Single celled Phylogenetic relationships not completely resolved Many very derived forms due to their life-style / habitat SU1 | pathogens – parasites - Protozoa fungal species disease Plasmodium falciparum malaria Trypanosoma brucei Sleeping sickness (Human African gambiense/rhodesiense trypanosomiasis) Trypanosoma crucii Chagas disease (American trypanosomiasis) Toxoplasma gondii toxoplasmosis Entamoeba histolytica amebiasis Giardia duodenalis, also known Giardiasis (Lambliasis) as Giardia intestinalis SU1 | pathogens – parasites – Metazoa multicellular Several major groups Helminths (worms) Platyhelminthes Cestoda Trematoda Nematoda Huge diversity of life cycles SU1 | pathogens – parasites - Metazoa Higher taxonomic level species disease Cestoda Taenia saginata (beef tapeworm) Taeniasis Zoonotic diseases Cestoda Taenia solium (pork tapeworm) Taeniasis, Cysticercosis Trematoda Schistosoma mansoni Schistosomiasis Trematoda Schistosoma haematobium Urogenital Schistosomiasis Nematoda Ascaris lumbricoides Ascariasis Nematoda Anclystoma, Necator Hookworm infection Zoonotic diseases infectious disease of humans that can jump from a non-human (usually a vertebrate) to a human and vice versa SU1 | pathogens – different grouping Instead of taxonomic grouping, we can group pathogens according to type of infection and tissue infected species intracellular extracellular tissue bacteria M. tuberculosis x lung bacteria S. pyogenes x Mouth, pharynx fungi C. albicans x Mouth, skin, genitals fungi Histoplasma capsulatum x Lung, spleen, lymphatic system Protozoa P. falciparum x Blood, liver Protozoa T. brucei x blood Nematoda Ascaris lumbricoides x intestines Nematoda Trichinella spiralis x x Striated muscle, intestines SU1 | pathogens – transmission v horizontal e r From parent to offspring Between members of same generation t Results in reduced virulence Results in increased virulence i c a l SU1 | pathogens – transmission Direct transmission – simple life cycle host pathogen host Indirect transmission – complex life cycle Intermediate host pathogen host pathogen host e n path hog ogen p at Vector host host SU1 | pathogens – transmission Direct transmission – simple life cycle Ascaris lumbricoides Indirect transmission – complex life cycle With intermediate host Schistosoma mansoni With involvement of vector Plasmodium falciparum SU1 | pathogens – direct transmission SU1 | pathogens – indirect transmission SU1 | pathogens – indirect (vectored) transmission SU1 | pathogens – transmission Transmission routes Fecal-oral Respiratory, droplets and aerosols Food-borne Sexually transmitted Skin contact SU1 | pathogens – transmission To enhance transmission, parasites use many different strategies Increase virulence Evade immune responses Manipulate host behaviour SU1 | overview of immune system Primary response Humoral immunity Secondary response – B cells subsequent exposure Antibodies Cell-mediated immunity T cells Immune messengers (cytokines) Physical and biochemical barriers Innate immune cells Immune messengers (cytokines) à inflammation SU1 | overview of immune system SU1 | overview of immune system Fast & non-specific Slow & specific & long-lasting SU1 | recognition self vs non-self MHC – major histocompatibility Antigen – anything that triggers an complex immune response All nucleated cells, also platelets, but not red blood cells SU1 | innate immunity Physical and chemical barriers protect body from invasion and include things like the skin and eyelashes substances at barriers (e.g. tears, mucous, blood clotting factors, stomach acid) stop and destroy them Chemical defenses (humoral defences) proteins able to interact directly or indirectly with invaders activating cascades of reactions to cause inflammation recruit further immune mediators that help to defend the body Examples include the complement system, interferons and interleukin-1 Cellular defenses identify things that are non-self, take steps to neutralize or destroy them activate the adaptive immune system Examples include phagocytes, natural killer cells and mast cells SU1 | innate immunity Extracellular pathogen Lack of MHC molecules pathogen-associated molecular patterns (PAMPs), common in many pathogens and absent in host recognition promotes their destruction through phagocytosis or cytotoxic killing Intracellular pathogen pattern recognition receptors (PRRs) detect non-self components, such as viral RNA, DNA or intermediate products production of pro-inflammatory cytokines, induces apoptosis of infected cells or flags them to be targeted by other innate immune cells for destruction SU1 | apoptosis Programmed cell death SU1 | white blood cells SU1 | phagocytotic cells Phagocytic cells (e.g. dendritic cells) chop up foreign material and present it on their surfaces important step in activating the adaptive immune response also known as antigen presenting cells (APCs). SU1 | innate immunity - summary main roles of the innate immune system are to: 1. Prevent the entry of foreign material using physical and chemical barriers 2. Prevent further spread of infection through humoral mediators such as the complement cascade 3. Remove non-self via phagocytosis (e.g., macrophages or neutrophils) or cytotoxic means 4. Activate the adaptive immune system through signalling cytokines and antigen presentation SU1 | adaptive immunity Organisms not born with adaptive immunity, not “hard wired” in their genes like innate immunity acquired during lifetime as a result of exposure to specific antigens through natural means (infection) or vaccination also known as acquired immunity adaptive immune response much slower than innate response days or even weeks to develop on first encounter (the primary immune response) specific to the antigen(s) present, can retain a long term “memory” enabling faster response if it is encountered again in the future Adaptive immunity does not necessarily last throughout entire lifespan, especially if not regularly re-exposed SU1 | adaptive immunity If innate immune system is insufficient to control foreign threat, adaptive immune system is activated via signaling molecules and/or the presentation of antigens by antigen presenting cells professional antigen presenting cells (e.g. dendritic cells) have major histocompatibility complex class II (MHC class II) molecules on their surface that are involved in the presentation of foreign peptides adaptive response consists of the cell-mediated immune response, which is executed by T cells, and the humoral immune response, which is controlled by activated B cells and antibodies Clonal expansion of T and B cells that specifically recognize epitopes of the antigens SU1 | clonal expansion SU1 | T cells, B cells SU1 | B cells SU1 | T cells, B cells