CONTENTS: 1. Introduction, 2. Host-Parasite Interaction, 3. Human Defense Mechanism , 4.Cells and Tissues of Immune System, 5. Synthesis and Structure of Antibodies, 6. Complement, 7. Pathogenic Microbes: Viruses, 8. Pathogenic Microbes: Bacteria, 9. Parasitic Protozoa: Entamoeba histolytica (Schaudinn. 1903), 10. Parasitic Protozoa: Trypanosoma (Gruby, 1843) 11. Parasitic Protozoa:Leishmania (Ross, 1903) 12. Parasitic Protozoa: Plasmodium (Marchiafava And Celli, 1885) 13. Parasitic Protozoa: Giardia lamblia (Lumbi, 1859) 14. Parasitic Protozoa: Trichomonas (Donne, 1837) 15. Platyhelminths : Fasciola hepatica ( Linnaeus, 1758) 16. Platyhelminths: Schistosoma (Weinland , 1858) 17. Taenia ( Linnaeus, 1758) 18. Parasitic Platyhelminths : Echinococcus (Rudolphi, 1801) 19&20. Parasitic Platyhelminths: Hymenolepis (Weinland, 1858) 21. Parasitic Nematodes: Ascaris lumbricoides ( Linnaeus, 1758) 22. Parasitic Nematodes : Hookworms 23. Parasitic Nematodes: Pinworm : Enterobius vermicularies ( Linnaeus , 1758 Leach, 1853 ) 24. Parasitic Nematodes : Dracunculus medinensis ( Linnaeus, 1758 Gallandant, 1773) 25. Parasitic Nematodes :Trichinella spirallis (Owen, 1835 Railliet, 1895) 26. Parasitic Nematodes : Wauchereria bancrofti ( Cobbold, 1877 Seurat, 1921).