Abstract : It is a pleasure to take this opportunity to express my deepest thanks and gratitude to my teacher, Professor Dr. Mohamed S. Zein, Head of the Department of Biochemistry for his continued interest, constructive criticism and the many valuable suggestions given generously throughout this work which is the result of his constant encouragement and learned guidance. Thanks also due to Dr. Mahmoud A. Zahran Ass. Prof. in the Biochemistry Department for his constant enthusiasm and precious help during the whole work. I owe special thank to Dr. Momtaz El-Sawy Ass. Prof. in the Clinical Pathology Department for his help and advice during the whole work to bring this thesis into final form. I am greatly indebted to Dr. Helmi H. Abaza Ass. Prof. in the Department of Tropical Medicine who kindly supplied the C.S.F. samples needed to carry out this thesis without which this work could not have been started. I am very greatful to Dr. M. Taky Lecturer of Public Health; for his help and advice concerning the statistical part of this work.