The adaptive immune system developed a strategy for monitoring the proteins synthesized in virtually any cell in the body, thereby preventing pathogens from ‘hiding out’ by adopting an intracellular lifestyle. To accomplish this, the immune system: Co-opted the ubiquitin-proteasome system used by cell for protein turnover Created a novel pathway using the immunoproteasome for generating peptides Created a novel pathway to express foreign proteins on the cell surface Took advantage of proteolytic enzymes present in endocytic vesicles

Complement proteins function in defense by _______. a. neutralizing toxins b. enhancing resident bacteria c. promoting inflammation d. forming pores that cause pathogens to disintegrate e. both a and b f. both c and d

The Adaptive Immune Response Is a Specific Defense Against Infection Describe the genetic basis of antibody diversity.

The Adaptive Immune Response Is a Specific Defense Against Infection In cystic fibrosis gene therapy, scientists propose the use of viral vectors to deliver normal genes to cells in the lungs. What immunological risks are involved in this procedure?

Cell-mediated responses work best against ________. a. pathogens inside cells b. pathogens outside cells c. toxins d. both b and c e. all are correct

Some cancer cells are insensitive to typical chemotherapy. Research into the mechanisms underlying this insensitivity uncovered an ability by these cells to pump the treatment drug out of the cell against its concentration gradient. Additional drugs have been developed that inhibit the pump, thus trapping the chemotherapeutic agent inside to promote cancer cell destruction. The Figure shows what happens when two types of cells are treated with a 3H-labeled anti-cancer drug, paclitaxel. Two additional drugs, imatinib and nilotinib, are evaluated for their ability to overcome the cancer cells ability to pump out the chemotherapeutic agent. An asterisk (*) indicates a statistically significant difference from the cells receiving paclitaxel alone. Do the additional drugs seem to the effective in over-coming the pump? Which set of graphs (A or B) best supports your answer? Explain your answer.

Antibiotics and Protein Synthesis Antibiotics are molecules produced by microorganisms as defense mechanisms. The most effective antibiotics work by interfering with essential biochemical or reproductive processes. Many antibiotics block or disrupt one or more stages in protein synthesis. Some of these are mentioned here. Tetracyclines are a family of chemically related compounds used to treat several types of bacterial infections. Tetracyclines interfere with the initiation of translation. The tetracycline molecule attaches to the small ribosomal subunit and prevents binding of the tRNA anticodon during initiation. Both eukaryotic and prokaryotic ribosomes are sensitive to the action of tetracycline, but this antibiotic cannot pass through the plasma membrane of eukaryotic cells. Because tetracycline can enter bacterial cells to inhibit protein synthesis, it will stop bacterial growth, helping the immune system fight the infection. Streptomycin is used in hospitals to treat serious bacterial infections. It binds to the small ribosomal subunit but does not prevent initiation or elongation; however, it does affect the efficiency of protein synthesis. Binding of streptomycin changes the way mRNA codons interact with the tRNA. As a result, incorrect amino acids are incorporated into the growing polypeptide chain, producing nonfunctional proteins. In addition, streptomycin causes the ribosome to randomly fall off the mRNA, preventing the synthesis of complete proteins. Puromycin is not used clinically but has played an important role in studying the mechanism of protein synthesis in the research laboratory. The puromycin molecule is the same size and shape as a tRNA/amino acid complex. When puromycin enters the ribosome, it can be incorporated into a growing polypeptide chain, stopping further synthesis because no peptide bond can be formed between puromycin and an amino acid, causing the shortened polypeptide to fall off the ribosome. Chloramphenicol was one of the first broadspectrum antibiotics introduced. Eukaryotic cells are resistant to its actions, and it was widely used to treat bacterial infections. However, its use is limited to external applications and serious infections. Chloramphenicol destroys cells in the bone marrow, the source of all blood cells. In bacteria, this antibiotic binds to the large ribosomal subunit and inhibits the formation of peptide bonds. Another antibiotic, erythromycin, also binds to the large ribosomal subunit and inhibits the movement of ribosomes along the mRNA. Almost every step of protein synthesis can be inhibited by one antibiotic or another. Work on designing new synthetic antibiotics to fight infections is based on our knowledge of how the nucleotide sequence of mRNA is converted into the amino acid sequence of a protein. Questions Why is targeting protein synthesis an effective strategy for preventing infection?

Describe how microfilaments and microtubules are involved in the phagocytosis and destruction of a pathogen by a macrophage.

The Adaptive Immune Response Is a Specific Defense Against Infection Identify the components of cellular immunity, and define their roles in the immune response.

A doctor is researching new ways to treat biofilms on artificial joints. Which approach would best help prevent bacterial colonization of the medical implants? Increase antibiotic dosing Create implants with rougher surfaces Vaccinate patients against all pathogenic bacteria Inhibit quorum sensing