The present book on Immunology is first in series written to cater the beginners in microbiology. The present book is designed to cater the needs of B.Sc. and M.Sc. students of Microbiology, Biotechnology and Pharmacy. The basic concepts of Immunology such as antigen, antibody, serological reactions, hypersensitivity are discussed concisely for better understanding of the students and form a source material to the teachers. Immunohematology, autoimmune disease and immunodeficiency are also covered precisely. The subject matter is written in simple language keeping in view of student's standard and very well illustrated with clear diagrams.