Immunology in an hour

1. Immunology in an hour

3. Immunity • Immunity • the state of protection from infectious disease • a less specific and a more specific component • Innate Immunity • the less specific component • the first line of defense against infection • mostly present before the onset of infection • constituting a set of disease-resistance mechanisms not specific to a particular pathogen • cellular and molecular components recognizing classes of molecules peculiar to frequently encountered pathogens innate immunity adaptive immunity

4. Nonspecific Defenses • Anatomic Barriers • Anatomic barriers → located at body surfaces (skin and mucosa) or within the body (endothelial cells and basement membranes) • partly effective in preventing virus spread but may be breached by large numbers of virus, by trauma, by increased permeability, by replication of virus in endothelial cells, or by transportation of virus in leukocytes. • Nonspecific Inhibitors • Body fluids and tissues → normally containing soluble viral inhibitors preventing viral attachment, directly inactivation of viruses, and others acting intracellularly. • may be overwhelmed by sufficient virus.

6. Phagocytosis • Viruses may be phagocytosed to different degrees by polymorphonuclear leukocytes and macrophages. • The effect of phagocytosis may be virus inactivation, persistence, or multiplication → consequently, the result may be clearance of virus, transportation to distant sites, or enhanced infection. • Fever • Replication of most viruses is reduced by even a modest rise in temperature. • During viral infection, fever can be initiated by several endogenous pyrogens, such as interleukins-1 and -6, interferon, prostaglandin E2, and tumor necrosis factor.

7. Inflammation • Inflammation → inhibiting viral replication through (1) elevated local temperature, (2) reduced oxygen tension, (3) metabolic alterations, and (4) acid production. • The effects of these mechanisms → often additive. • The four cardinal signs of inflammation • heat (calor), • redness (rubor) from local vessel dilation, • swelling (tumor) from influx of proteins and cells, • and pain (dolor) from the triggering of local nerve endings due to vasoactive products and increased tissue pressure

8. detected by pattern recognition molecules of the host taken up by phagocytic cells pathgens inside the specific response; the adaptive (acquired) immune response invading pathogens breaching the host’s physical and chemical barriers Inflammation

9. Viral Interference and Interferon • Viral interference → infection by one virus → cells resistant to the same or other superinfecting viruses. • Interference → usually mediated by newly induced host cell proteins designated as the interferon systems. • Secreted interferon → binding to cells and induces them to block various stages of viral replication.

10. breaching the barriers (the first hurdle for a pathogen) • obvious barriers • the skin and the mucosal membranes • the acidity of the stomach contents and of perspiration • enzymes, such as lysozyme, attacking the cell wall • breaching of the barriers • bites of animals or insects • puncturing the skin → a number of diseases • rabies or tetanus (animal bites) • malaria (mosquitoes) • plague (fleas) • Lyme disease (ticks) • a dramatic example of barrier loss; in burn victims→ lost the protective skin and aggressive treatment required

11. beyond the primary barrier • Phagocytic cells • demonstrated by Metchnikoff • ingestion of extracellular particulate material by phagocytosis (one type of endocytosis) • phagocytosis; conducted by specialized cells, such as blood monocytes, neutrophils, and tissue macrophages • mostly capable of other forms of endocytosis, such as receptor-mediated endocytosis and pinocytosis • Soluble molecules • the protein lysozyme • the interferon proteins • components of the complement system • collectins (killing certain bacteria directly by disrupting lipid membranes or by aggregating them to enhance susceptibility to phagocytosis) • Toll-like receptors (pattern recognition)

12. Toll-like Receptors • pattern recognition • recognizing a given class of molecules • certain types of molecules unique to microbes and never found in multicellular organisms; immediate recognition and combating invaders→ a strong feature of innate immunity • molecules with pattern recognition • (maybe) soluble, or • cell-associated receptors, such as those designated the Toll-like Receptors (TLRs)

14. Pathogen-associated molecular pattern receptor signaling Leucine rich repeat (LRR) Interferon production Boxes 1, 2, and 3 highly conserved, and binding sites for intracellular proteins participating in the signaling pathways mediated by TLRs Toll/IL-1 Receptor (TIR)

16. Toll-like receptors • membrane-spanning proteins sharing a common structural element in the extracellular region • repeating segments of 24 to 29 amino acids containing the sequence xLxxLxLxx (x, any amino acid; L, leucine) – leucine-rich repeats (LRRs) • all TLRs; several LRRs • a subset of the LRRs making up the extracellular ligand-binding region of the TLR • The intracellular domain of TLRs; the TIR domain Toll/IL-1 receptor, referring to the similarity to the region of a IL-1 receptor • boxes 1, 2, and 3; highly conserved, and binding sites for intracellular proteins participating in the signaling pathways mediated by TLRs

17. 13 TLRs as of March, 2009

18. TLR6 TLR1 (TIL) TLR10 TLR2 (TIL-4) TLR8 Phylogenetic tree of the human TLRs TLR7 TLR9 TLR3 TLR5 (TIL3) TLR4 (Toll)

20. TLRs and Ligands • TRL1; bacterial multiple triacyl lipopeptides • TRL2; • bacterial multiple glycolipids, multiple lipopeptides, multiple lipoproteins, lipoteichoic acid • host cell HSP70 • fungal zymosan • numerous others • TLR3 (double-stranded RNA, poly IC) • TLR4; lipopolysaccharide, several heat shock proteins, fibrinogen, heparan sulfate fragments, hyaluronic acid fragments, numerous others • TLR5; flagelin

21. TLR6; multiple diacyl lipopeptides (mycoplasma) • TLR7; imidazoquinoline, loxoribine (a guanosine analogue), bropirimine, single-stranded RNA • TLR8;small synthetic compounds, single stranded RNA • TLR9; unmethylated CpG, DNA • TLR10; unknown • TLR11; Profilin (uropathogenic bacteria) • TLR12; unknown • TLR13; unknown

22. signalling factors, called cytokines → inflammation phagocytosis of bacterial pathogens → digestion →Ag presentation viral factors; shut down of protein synthesis may undergo programmed cell death (apoptosis); maybe releasing antiviral factors such as interferons microbial lignads activation host cell The discovery of the Toll-like receptors finally identified the innate immune receptors that were responsible for many of the innate immune functions that had been studied for many years. Interestingly, TLRs seem only to be involved in the cytokine production and cellular activation in response to microbes, and do not play a significant role in the adhesion and phagocytosis of microorganisms.

24. Myd88 • originally discovered and cloned by Drs Dan A Liebermann and Barbara Hoffman as “Myeloid Differentiation primary response gene 88” • a universal adapter protein → used by all TLRs (except TLR 3) to activate transcription factor NF-kappa B. • Mal (also known as TIRAP) → necessary to recruit Myd88 to TLR 2 and TLR 4, and MyD88 then signals through IRAK. • MYD88→ its human gene and seems to function similarly, since the immunological phenotype of human cells deficient in MyD88 is similar to cells from MyD88 deficient mice, though available evidence suggests that MyD88 is dispensable for human resistance to common viral infections and to all but a few pyogenic bacterial infections, demonstrating a major difference between mouse and human immune responses.

25. Toll-like Receptors • the protein Toll • the first attraction of attention; during the 1980s • essential for the development of a proper dorsal-ventral axis in Drosophila melanogaster • Toll, referring to the mutant flies’ bizarrely scrambled anatomy, meaning “weird” in German slang • a transmembrane signal receptor protein • related molecules with roles in innate immunity known as Toll-like receptors (TLRs) • Three recent discoveries → ignited an explosion of knowledge about the central role of TLRs in innate immunity

26. Jules Hoffman and Bruno Lemaitre, 1996 • mutations in Toll; making flies highly susceptible to lethal infection with Aspergillus fumigatus • wild type files – immune • convincingly demonstrating the importance of pathogen-triggered immune responses in a nonvertebrate organism • Ruslan Medzhitov and Charles Janeway, 1997 • a certain human protein → activating the expression of immune response genes when transfected into a human experimental cell line • identified by homology by its cytoplasmic domain homologous to Toll → subsequently named TLR4 • the first evidence of the conserved immune response pathway between fruit flies and humans

27. Bruce Beutler, 1998 • studies with mutant mice • TLRs → part of the normal immune physiology of mammals DNA sequencing → the lps gene encoding a mutant form of a Toll-like receptor, TLR4, different only in a single amino acid homozygous lps locus resistant to LPS (Endotoxin) TLR4, indispensable for the recognition of LPS → a role in normal immunophysiology

28. references for Toll gene episodes • Originally identified in the fruit fly Drosophila melanogaster in 1985 • Their name derives from ChristianeNüsslein-Volhard's 1985 exclamation, "Das war ja toll!" (“Toll” is German for “amazing” or “mad”) • first identified as a gene important in embryogenesis in establishing the dorsal-ventral axis • Hashimoto C, Hudson KL, Anderson KV (1988). "The Toll gene of Drosophila, required for dorsal-ventral embryonic polarity, appears to encode a transmembrane protein". Cell 52 (2): 269–79. • Hansson GK, Edfeldt K (2005). "Toll to be paid at the gateway to the vessel wall". Arterioscler. Thromb. Vasc. Biol. 25 (6): 1085–7. • found to have a role in the fly’s immunity to fungal infection in 1996 – required for innate immunity • Lemaitre,B., Nicolas,E., Michaut,L., Reichhart,J.M., and Hoffmann,J.A. 1996. The dorsoventral regulatory gene cassette spatzle/Toll/cactus controls the potent antifungal response in Drosophila adults. Cell 86:973-983. • TLRs in mammals; first identified by RusianMedzhitov and Charles Janeway in 1997 • Medzhitov R, Preston-Hurlburt P, Janeway CA (1997). "A human homologue of the Drosophila Toll protein signals activation of adaptive immunity". Nature 388 (6640): 394–7.

29. The role of Hox genes in development

31. Innate and Adaptive Immune Responses

33. Adapted Immunity of Host

34. adaptive immunity Innate Immunity in general, most of the microorganisms encountered by a healthy individual readily cleared within a few days by defense mechanisms of the innate immune system before the activation of the adaptive immune system • the broad reactivity • uniform in all members of a species Adaptive Immunity • not coming into play until the recognition of antigenic challenge to the organism • responding to the challenge with a high degree of specificity as well as the remarkable property of “memory”

35. soluble proteins Collaboration between innate and adaptive immunity increasing immune responsiveness • the innate and adaptive immune systems • no independent operation • functioning as a highly interactive and cooperative system • producing a combined response more effectively • certain cellular and molecular components playing important roles in both types of immunity • Macrophages and microbes receptor adaptive immune response eliminating pathogens microbes M

36. The Soluble Proteins (the soluble mediators) • growth factor-like molecules, known by the general name cytokines • cytokines • reacting with receptors n various cell types • signaling the cell to perform functions such as • synthesis of new factors • undergoing differentiation to a new cell type • chemokines • a restricted class of cytokines • chemotactic activity recruiting specific cells to the site of the cell secreting that cytokine; chemokines • Signaling: the type of intracellular communication mediated by cytokines

37. Ag lymphokine Th cells IL-2 Th1 cells activated T and B, NK, macrophages, oligodendrocytes Macrophage monokine IL-1 Macrophages, B cells, monocytes, dendritic cells Th, B, NK, macrophages, endothelium, and others

38. Platelet Buffy Coat Granulocyates, RBC Monocytes Lymphocytes 

39.    * * Globulin Albumin * Antibody =  globulin Serum Blood cells Blood RBCs WBCs Lymphocytes B cells T cells Macrophages Mono cytes Granulocytes G/M Neutrophils Eosinophils Basophils plasma Megakaryocytes Platelets