This 4th edition is thoroughly updated version of the 3rd edition with its intact simple to-the-point presentation of knowledge, which makes the book examination friendly. This edition will be useful not only to the undergraduates, but also to the postgraduates, immunologists and geneticists. - A chapter on "Stem Cell Therapy" - Inclusion of Summary at the end of each chapter - The concept of personalized medicine under Pharmacogenetics - Information updation in nearly all chapters - A chapter on "Stem Cell Therapy" - Inclusion of Summary at the end of each chapter - The concept of personalized medicine under Pharmacogenetics - Information updation in nearly all chapters