ENVIRONMENTAL INDUCTION AND GENETIC-CONTROL OF SURFACE-ANTIGEN SWITCHING IN THE NEMATODE CAENORHABDITIS-ELEGANS

Nematodes can alter their surface coat protein compositions at the mol ts between developmental stages or in response to environmental change s; such surface alterations may enable parasitic nematodes to evade ho st immune defenses during the course of infection. Surface antigen swi tching mechanisms are presently unknown. In a genetic study of surface antigen switching, we have used a monoclonal antibody M37, that recog nizes a surface antigen on the first larval stage of the free-living n ematode Caenorhabditis elegans, We demonstrate that wild-type C. elega ns can be induced to display the M37 antigen on a later larval stage b y altering the growth conditions, Mutations that result in nonconditio nal display of this antigen on all four larval stages fall into two cl asses. One class defines the new gene srf-6 II. The other mutations ar e in previously identified dauer-constitutive genes involved in transd ucing environmental signals that modulate formation of the dauer larva , a developmentally arrested dispersal stage. Although surface antigen switching is affected by some of the genes that control dauer formati on, these two processes can be blocked separately by specific mutation s or induced separately by environmental factors, Based on these resul ts, the mechanisms of nematode surface antigen switching can now be in vestigated directly.