Question

51.- NKs

52.- Immunological memory: Primary vs Secondary.

53.- Passive and Active Immunity. Types of Acquire or adaptive immunity.

54.- Acquire Immunodeficiency Syndrome (AIDS): The origin of AIDS. HIV infection. Subtypes of HIV. Stages of HIV infection. Resistance to HIV. Impact of age on survival. Exposed, but not infected, population. Long-term survivors.

55.- HIV Diagnosis, Prevention and Treatment. Worldwide epidemiology.

56.- Bacterial Diseases in the Nervous System: Listeriosis. Clinical aspects. Diagnosis. Prevention, and Treatment.

57.-Bacterial Diseases in the Nervous System: Bacterial Meningitis: Haemophilus influenzae, Neisseria meningitides, and Streptococcus pneumoniae. Clinical aspects. Diagnosis, Prevention, and Treatment.

58.- Viral Diseases in the Cardiovascular and Lymphatic Systems: Burkitt’s Lymphoma, Severe Dengue, Marburg virus, Lassa virus, Ebola virus and Hanta virus. Clinical aspects, Diagnosis, Prevention, and Treatment.

59.- Microbial Diseases of the Upper Respiratory System: Bacterial: Streptococcal Pharyngitis, Scarlet Fever, Diphteria, and Otitis Media. Clinical aspects, Diagnosis, Prevention and Treatment.

60.- Microbial Diseases of the Lower Respiratory System: Viral: Common cold, Pertussis, Viral pneumonia, Respiratory Syncytial virus, Influenza virus. Clinical aspects, Diagnosis, Prevention, and Treatment. Antigenicity of Influenza virus. Influenza vaccine. Tuberculosis: Pathogenesis, Diagnosis, Treatment of Tuberculosis. Testing for Drug Susceptibility. Vaccines. Bacterial pneumonia: Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae. Clinical aspects, Diagnosis, Prevention, and Treatment.

61.- Bacterial Diseases of the lower Digestive System: Staphylococcal. Food poisoning. Shigellosis. Salmonellosis. Typhoid fever. Cholera. Noncholera vibrios. Escherichia coli Gastroenteritis. Campylobacter Gastroenteritis. Helicobacter pylori: Peptic ulcer Disease. Clostridium difficile. Clinical aspects, Diagnosis, Prevention, and Treatment.

62.- Viral Diseases of the Digestive System: Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, and Hepatitis E viruses. Clinical aspects, Diagnosis, Prevention, and Treatment.

63.- Bacterial Diseases of the Urinary system: Cystitis, Pyelonephritis, Clinical aspects, Diagnosis, Prevention, and Treatment.

64.- Infectious Diseases of the Reproductive System: Neisseria gonorrheae, Nongonococcal urethritis (NGU). Chlamydia trachomatis. Pelvic inflammatory disease. Syphilis. Genital Herpes virus, Human papilloma virus, Candida albicans, Trichomonas vaginalis. Clinical aspects, Diagnosis, Prevention, and Treatment.

Answer 1

NATURAL KILLER CELLS (NKs)

• NK cells are large granular lymphocytes that constitute 10 - 15% of peripheral blood lymphocyte
• They are derived from a seperate lymphoid lineage.
• They are cytotoxic but antigen non-specific
• They are part of innate immunity, act as first line of defense and donot require prior contact with the antigen
• NK cells donot differentiate into memory cells
• They act against virus infected cells and tumour cells till the cytotoxic T cells are activated and take over the function

Mechanism of NK cell mediated cytotoxicity

1.Receptor interaction

They directly recognize certain ligands present on the surface of altered host cells like virus infected cells or tumour cells which is also present in normal cells.Still NK cells can distinguish between host cells and the altered cells.This is mediated by by two types of receptors present on NK cell surface ( Theory of opposing signals model ).

• Activation receptors ( e.g. NKR-P1, CD16 ): When these receptor are are engaged with ligands present on the target cells; NK cells become activated
• Inhibitory receptors: Binding of inhibitory receptors to MHC -1 molecule generate an inhibitory signal that suppress the NK cells even if they are bound to the activation receptors.However in virus inffected cells and tumour cells, the MHC-1 expression is remarkably reduced.In such cases, there would not be any inhibitory signal.Hence binding of activation receptor to its ligands leads to activation of NK cells.

2.Target cell distruction

• It is by secreting perforins and granzymes.
• Perforin forms pores on target cells through which granzymes enter and lyse the target cells.

3.Alternate mechanism of NK cell activity

• NK cells respond to IL-12 produced by macrophage and secrete IFN-gamma, which inturn activates the macrophages.Activated macrophages phagocytose and kill the microbes