The gastro-intestinal (GI) nematode Heligmosomoides polygyrus is an important experimental model in laboratory mice and a well-studied parasite of wood mice in the field. Recent advances in basic immunology and biotechnology with the concomitant development of well-defined laboratory models of infection, immunoparasitologists, have more precisely analyzed and defined the different immune effector mechanisms during the infection resulting in great improvement in our current knowledge and understanding of protective immunity against gastrointestinal (GI) nematode parasites. Development of vaccines against gastrointestinal nematodes is essential to control the parasite infection. As of yet, no vaccine has been made commercially available to producers. The present study deals with the role of eosinophils, lymphocytes and basophils in modulation of immune response during primary infection in control mice with H. polygyrus at different stages of infection, and their role in imparting protective immunity in vaccinated mice during challenge infections.