1. Chapters 16 and 17
Nonspecific and Specific Defenses of the Host

2. The Concept of Immunity
Susceptibility: lack of resistance to a disease
Immunity: ability to fight off disease
Innate immunity (nonspecific): built in defenses against any pathogen
Adaptive immunity (specific): resistance to a specific pathogen

3. An Overview of the Body’s Defenses
Nonspecific
Specific
Figure 16.1

4. Nonspecific Defenses of the Host
A. Skin and mucous membranes
Epithelial tissue
Waterproof yet elastic
Mucous membranes produce mucus

5. Epidermis consists of tightly packed cells with
Skin
Epidermis consists of tightly packed cells with
Keratin, a protective protein
Figure 16.2

6. Nonspecific Defenses of the Host
Mucous membranes
Mucus: Traps microbes
Ciliary escalator: Microbes trapped in mucus are transported away from the lungs

7. Ciliary Escalator
Figure 24.7

8. Ciliary Escalator
Figure 16.4

9. Nonspecific Defenses of the Host
B. Physical Barriers
Lacrimal apparatus: tears wash eye
Saliva: Washes microbes off
Urine
Vaginal secretions
Hairs
Ciliated cells + mucus

10. Lacrimal Apparatus
Figure 16.3

11. Nonspecific Defenses of the Host
C. Chemical Defenses
Lysozyme
Gastric juices
Digestive enzymes
pH – stomach (pH 1-3), skin and vagina (pH 3-5)
Sebum/wax
Perspiration
Transferrins – bind iron in blood
Complement – bind to pathogens or increase immune response
Interferons

12. Interferons (IFNs)
IFN- and IFN-: Cause cells to produce antiviral proteins that inhibit viral replication
Gamma IFN: Causes neutrophils and macrophages to phagocytize bacteria

13. Nonspecific Defenses of the Host
D. Normal flora – outcompete pathogens/ produce bacteriocins, etc.
Where are they found?
Skin
Eyes
Nose/throat
Mouth
Large intestine
Vagina
Lower urethra

15. Nonspecific Defenses of the Host
E. Phagocytic cells
1. Neutrophils
2. Monocytes/macrophages

16. Phagocytosis Phago: From Greek, meaning eat
Cyte: From Greek, meaning cell
Ingestion of microbes or particles by a cell, performed by phagocytes
Figure 16.6

17. Phagocytosis
Figure 16.7

18. Microbial Evasion of Phagocytosis
Inhibit adherence: M protein, capsules
Streptococcus pyogenes, S. pneumoniae
Kill phagocytes: Leukocidins
Staphylococcus aureus
Lyse phagocytes: Membrane attack complex
Listeria monocytogenes
Escape phagosome
Shigella, Rickettsia
Prevent phagosome-lysosome fusion
HIV, Mycobacterium tuberculosis
Survive in phagolysosome
Coxiella burnettii

19. Nonspecific Defenses of the Host
F. Inflammation
Heat
Swelling (edema)
Pain
Redness
Loss of function (sometimes)
Purpose: 1. destroy pathogen
2. if not, then wall off pathogen
3. repair tissues

20. The Process of Inflammation
Figure 16.8a, b

21. Phagocyte Migration and Phagocytosis
[Insert Animation Inflammation: Overview, Steps.]
Figure 16.8c

22. Tissue Repair
Figure 16.8d

23. Nonspecific Defenses of the Host
G. Fever
Normal body temp. = 37oC (set by hypothalamus)
Increase in temp. = destruction of pathogens; enhancement of immune response

24. Specific Defenses Humoral Immunity B cells – produce antibodies (Ab)
Ab bind to antigens
Antigens (Ag) are any type of molecule which elicits an immune response

28. Specific Defenses
Cellular Immunity T cells- CD8 Cytotoxic T cells – killers CD4 Helper T cells – communicators

31. Specific Defenses
Memory cells are produced after challenge to immune system by pathogen or vaccination
2nd response is greater, faster

32. HIV/AIDS Review the websites
Most common cause of exposure to HIV of healthcare workers –
accidental needle stick
Health professional with greatest number of cases of HIV acquired on the job –
Nurse

33. Adults reported with AIDS and a history of employment in healthcare, where job is known, by occupation, as of December 2002.
Occupation
Number
Nurses
5,378
Health aides
5,638
Technicians
3,182
Physicians
1,792
Therapists
1,082
Dental workers
492
Paramedics
476
Surgeons
122
Other
5,050
Total
23,212
“Surveillance of Healthcare Personnel with HIV/AIDS, as of December 2002”,

34. Healthcare personnel with documented and possible occupationally acquired AIDS/HIV infection, by occupation, as of December 2002.
Occupation
Documented
Possible
Nurse 24 35
Laboratory worker, clinical 16 17
Physician, nonsurgical 6 12
Laboratory technician, nonclinical 3 -
Housekeeper/maintenance worker 2 13
Technician, surgical
Embalmer/morgue technician 1
Health aide/attendant 15
Respiratory therapist
Technician, dialysis
Dental worker, including dentist
Emergency medical technician/paramedic
Physician, surgical
Other technician/therapist 9
Other healthcare occupation 5
Total 57
139
“Surveillance of Healthcare Personnel with HIV/AIDS, as of December 2002”,

35. HIV/AIDS
Type of pathogen – human immunodeficiency virus Disease – Acquired immune deficiency syndrome Transmission – bodily fluids, in utero; behaviors – unprotected, non-monogamous sex, sharing of needles, pregnancy Prevention – change behaviors, prophylactic treatment of a pregnant woman Treatment

37. Classes of HIV/AIDS Antiretroviral Drugs
Reverse Transcriptase (RT) Inhibitors interfere with the critical step during the HIV life cycle known as reverse transcription.
Nucleoside/nucleotide analogs are faulty DNA building blocks. When these faulty pieces are incorporated into the HIV DNA (during the process when HIV RNA is converted to HIV DNA), the DNA chain cannot be completed, thereby blocking HIV from replicating in a cell.
Protease Inhibitors interfere with the protease enzyme that HIV uses to produce infectious viral particles.
Fusion/Entry Inhibitors interfere with the virus' ability to fuse with the cellular membrane, thereby blocking entry into the host cell.
Integrase Inhibitors block integrase, the enzyme HIV uses to integrate genetic material of the virus into its target host cell.
Multidrug Combination Products combine drugs from more than one class into a single product. To combat virus strains from becoming resistant to specific antiretroviral drugs, healthcare providers recommend that people infected with HIV take a combination of antiretroviral drugs known as highly active antiretroviral therapy (HAART). Developed by NIAID-supported researchers, the HAART strategy combines drugs from at least two different antiretroviral drug classes.

38. HIV/AIDS Replication of virus Attachment Penetration Uncoating
Reverse transcription
Integration of viral DNA into host chromosome
Transcription of viral DNA to RNA
Translation of RNA to viral proteins
Assembly of new viruses
Budding through host membrane

40. The End