ADDING 1. This class is open. Students may add this course on a first come, first served basis via WebReg during the first two full weeks of the quarter (January 3 rd - 14 th ). (NOTE: If this class was previously CLOSED and you were on a wait list, you will need to drop yourself from the wait list in order to add the class.) The last day to add is Friday, January 14 th . 2. I cannot sign add cards for students who wish to add except if the student is a concurrent enrollment student. Concurrent Enrollment add cards will only be signed during the 3 rd week of the quarter if spaces are available. Students in need of pre-requisite overrides should send an email to me including student name and PID. 3. WITHDRAWAL PROCESS The last day to drop a class without a “W” is Friday, January 28 th and the last day to drop a class with a “W” is Friday, March 4 th .Please direct all Add/Drop inquiries to Student Affairs at x40557. Add-Drop Instructions Immunology BICD 140 Winter 2005
Discussion Sections - Immunology BICD 140 Winter 2005 Sections will discuss lectures, homework assignments, and exams. You must choose one discussion section and hand in your homework to your designated TA. Section Day Time (50') Room TA Email A01 TBA TBA TBA Laura [email_address] A02 Thurs 6:00 PM CENTR 217b Adam [email_address] A03 Thurs 5:00 PM CENTR 218 Lauren [email_address] A05 Fri 08:00 AM CENTR 218 Matt [email_address] A06 Fri 10:00 AM CENTR 220 Hart [email_address] A04 Fri 11:00 AM CENTR 218 " Note: This page will be updated to show the correspondence between TAs and Discussion Sections
Web Site Username: bicd Password: 140 PLEASE READ “COURSE INFORMATION” If you do not check the e-mail address listed by the registrar, you will not receive course announcements http://hedricklab.ucsd.edu/BICD140 Note: site for last year’s course:
Grading: Two midterm exams each worth 100 points One final worth 150 points The homework grade (100 points total) will be automatically substituted for your lowest midterm! However, you must take both midterms. If you have a valid excuse to miss a midterm (e.g., death in family, severe illness, car accident on the way to school), drop off a note signed by a relevant official to Mandy Butler’s Office, York 3080. In that case, your homework will substitute for the missing midterm. Do not miss a midterm without a valid excuse. There will be no make-up midterms. You must take the final. If you have a conflict with the Final date, let me know immediately.
Innate vs. Acquired Immunity- conceptual and practical difference
How does innate immunity work?
(Chapter 7 and 8 dealing with complement and innate immunity)
Lecture 1 Introduction to immunology
The word IMMUNITY Derives from the latin immunitas , meaning freedom from public service (i.e., the military draft). From Merriam-Webster dictionary: “ a condition of being able to resist a particular disease especially through preventing development of a pathogenic microorganism or by counteracting the effects of its products”
HOST DEFENSE= Innate + adaptive immunity Resistance to infection can be learned or innate. It appears that many organisms lack learned immunity, but can have robust innate defenses. As we shall see, learned immunity is an evolutionary offshoot of innate immunity, and the human immune system combines both types in host defense. There are two kinds of immunity
The Triumph of Death - Pieter Brueghel the Elder ca. 1562
Big bugs have little bugs Upon their backs to bite ‘em Little bugs have littler bugs And so on ad infinitum - Ogden Nash Colonization of large organisms by smaller organisms or viruses is the “ inverse food chain” Large complex organisms present a source of energy and a habitat for smaller organisms and viruses via colonization Colonization and defense against colonization is a fundamental principle in biology The immune system is principally and most importantly evolved to sculpt colonization to benefit the host Every organism needs host defense
Concept 1 Every organism needs to distinguish self from non-self because everyone has a parasite Case study: bacteria
Adapted from Murray NE. Microbiology. 2002, 148:3-20. Bertani, G. & Weigle, J. J. (1953) E. coli strain C is sensitive to phage grown in either strain K-12 or C. Efficiency of growth 100% E. coli strain K-12 is resistant to phage grown in E. coli strain C Efficiency of growth 0.02% E. coli Strain K-12 Efficiency of growth 100% bacteriophage Bacteria have innate immunity (and tolerance) to bacteriophage E. coli Strain C Efficiency of growth 100% restriction
What “restricted” the phage growth? Restriction enzymes 5’...GAATTC...3’ 3’...CAATTG...5’ Example EcoRI target sequence
EcoR1 methylase modifies host DNA EcoR1 restriction endonuclease cuts incoming bacteriophage DNA NOT methylated DNA A chemical difference between self and foreign is distinguished Strategy: mark “self” DNA and destroy “non-self” DNA Murray NE. Microbiology. 2002, 148:3-20. Type 2 restriction/ modification system of bacteria
Concept 2 Distinguishing self from non-self may require “marking” of self
Eco K1 TG A me (N) 8 TGCT ACT (N) 8 A CGA If hemimethylated methylates other strand Eco K1 TG A (N) 8 TGCT ACT(N) 8 A CGA If UN-methylated, cuts (nearby but not in sequence) Type 1 restriction/ modification enzyme complex Q: what happens during DNA synthesis?
EcoKI recognizes the sequence 5'...AAC(N) 6 GTGC...3' EcoBI recognizes the sequence 5'...TGA(N) 8 TGCT...3’ (K12 has two other restriction enzymes as well!) Redundancy: An individual bacterium can carry multiple restriction modification enzymes with different specificities Example, E.coli strain K12 carries these two class II restriction enzymes Q: what is the evolutionary selection for this redundancy? Probability of a particular 7 nucleotide sequence is 4 7 =1/16,384 Genome sizes of bacteriophage range from 5,000-100,00 base pairs Bacteriophage can potentially avoid certain restriction sites.
Concept 3 Defense mechanisms must be redundant to reduce the likelihood of escape by the parasite.
Phage escape mechanisms
reduce genome size
eliminate certain nucleotide sequences carrying the restriction site
be single stranded, requiring replication of the second strand (and attendant methylation) prior to forming a double stranded substrate (restriction enzymes are dimers that require double stranded DNA, whereas methyltransferase work as monomers).
Recognition Sequence Enzymes AA/CGTT Acl I Arthrobacter luteus A/AGCTT Hind III Haemophilus influenzae Causitive agent of bacterial influenzae. A/CATGT Pci I Planococcus citreus A/CCGGT Age I Agrobacterium gelatinovorum ACCTGC(4/8) BspM I Bacillus sphaericas A/CGCGT Mlu I Micrococcus luteus “ A bacterium that degrades the compounds in sweat into ones producing unpleasant odors.” A/GATCT Bgl II Bacillus globigii AG/CT Alu I Arthrobacter luteus AGG/CCT Stu I Streptomyces tubercidicus AGT/ACT Sca I Streptomyces caespitosus . . . . Virtually all bacteria have restriction/modification systems
Diversity Restriction enzymes have been found only within prokaryotes. Many thousands of bacteria and archae have now been screened for their presence. Analysis of sequenced prokaryotic genomes indicates that they are common--all free-living bacteria and archaea appear to code for them. Restriction enzymes 3706 ~250 different sequences seen Type I 59 Type II 3634 Methyltransferases 757 Type I 49 Type II 595 (information from a supplier of restriction enzymes, NEB) Note: Most type 2 RE see palindromic sequences and recognize 4-8 bp seque nces. There is a natural restriction enzyme for practically every conceivable such palindrome.
Concept 4 Defense mechanisms can force parasite specialization. Example: Phage T5 produces a protein that blocks EcoRI enzymatic activity.
E. coli Strain K-12 E. coli Strain C Efficiency of growth 100% Efficiency of growth 100% Efficiency of growth 100% Efficiency of growth 0.02% bacteriophage Q: what happens to a bacterium that loses its methylase gene? Carries restriction/modification system r + m + r - m - Adapted from Murray NE. Microbiology. 2002, 148:3-20.
Concept 5 Defense mechanisms can be toxic to self if not properly controlled Deletion of the modification enzyme without concomiant elimination of the restriction enzyme would be lethal. Restriction and modification enzyme genes are always found closely linked in the bacterial genome. This probably minimizes the risks associated with DNA deletion.
Concept 6 Defense mechanisms can affect interactions with other individual of the same species Restriction enzymes also can block bacterial conjugation (between incompatible strains). Conjugation is a DNA transfer between bacteria that is analagous to sex.
Every organism needs host defense Example: bacteria 1. There is a need to distinguish self from non-self because everyone has a parasite. 2. Distinguishing self from non-self often requires “marking” of self. 3. Defense mechanisms must be redundant to reduce the likelihood of escape by the parasite. 4. Defense mechanisms can force parasite specialization. 5. Defense mechanisms can be toxic to self if not properly controlled. 6. Defense mechanisms can affect interactions with other individual of the same species.
Thucydides: “History of the Peloponnesian War” 5th century BCE He noted that during the plague of Athens (430 BCE) the sick were nursed by those who had recovered from the disease (caused by a bacterium, possibly Yersinia pestis ) because they knew that they were safe from developing, or at least dying from, the disease a second time. It was also clear that this resistance was specific to the plague disease only. Thus the specificity and memory of immunity was recognized long ago. The notion of immunity to disease is ancient
Immunizations have been carried out for a long time Variolation was an ancient folk practice of vaccination to smallpox (infectious agent Variola major virus) practiced throughout Asia, Africa, and parts of Europe. Essentially, it followed a procedure in which blisters from diseased skin carrying virus from a smallpox victim was innoculated in the skin or nose. Variolation became a common practice in England after the Prince and Princess of Wales had their children innoculated in 1722. The precursor to the modern vaccine was based on the work of Jenner, who showed in 1798 that pustules from cows diseased with cowpox had the same smallpox protective effect. Hence vaccination (Latin vaccus, cow).
Germ theory and the scientific basis of immunity Jenner didn’t know why or how his vaccine worked. In the 1870s Robert Koch, Louis Pasteur, and others identified specific microbial agents of several human and animal diseases, including Anthrax (Bacillus anthracis), cholera ( Vibrio cholerae ) , tuberculosis ( Mycobacterium tuberculosis ), Dyptheria ( Corynebacterium diphtheriae ) and the Plague ( Yersinia pestis ). A major breakthrough was Pasteur’s demonstration that injection of weakened pathogenic microbes of Anthrax or fowl cholera could protect animals from lethal infection of the same microbe. “Attenuated” vaccines are commonly used today. He later developed an effective rabies vaccine using ground up spinal tissue from diseased animals. However, vaccines against some microbes, such as tuberculosis, failed, and an effective vaccine is still not available for this and many other important diseases.
Some vaccines really work! Particulary effective are vaccines that protect from viruses that require human-to-human transmission Smallpox * * * *human to human transmission Fig 1.1 Parham Fig 1.27 Parham
“ Innate immunity” evolves with the germline and involves receptors, enzymes and cells that detect conserved aspects of microbes and parasites. Examples: lysozyme in the eye that digests bacterial peptidoglycan, antibacterial peptides produced by epithelia, receptors for formyl-methionine or lipopolysaccharides on phagocytic cells, the complement system.
“ Adaptive immunity” is provided by lymphocytes and evolves not only in the germline, but also in the soma, providing immunity with its hallmark properties of memory, specificity, and self-tolerance.
Cells of the immune system Thymus Adaptive Innate Naïve, resting lymphocytes in lymph nodes, spleen Bone marrow/fetal liver Fig 1.27 Parham
Analogies between host defense and homeland defense
Highly complex, redundant, involving overlapping responsibilities, distinct specializations, information sharing and several levels of communication between components.
Military (several types), police (several), port authorities (several), intelligence, hospitals, communications at different levels, indentification systems, central and local government coordination. Running the system is expensive, wasteful, and at any given time, many components appear to be inactive.
Innate immunity is manifest in many cells of the body. The basis is the recognition of molecular patterns , that occur in microbes but not animals (e. g., unmethylated DNA sequences, dsRNA, cell wall components, etc)
This is the bedrock of immunity in all organisms--even bacteria have defense mechanisms against bacterial viruses