The present invention relates to methods and materials for modulating the complement alternative pathway (CAP), the complement classical pathway (CCP), the complement lectin/mannose pathway (CMP), or combinations thereof, as well as methods and materials for targeting diagnostic, prophylactic and therapeutic agents to localized areas of tissue within the body where they may more directly exert their effects upon the intended target cells or tissue, with reduced, associated systemic effects compared with administration of the same or similar agents in an untargeted, systemic manner. The methods and materials of the present invention may therefore allow for increased efficacy, lower threshold effective dosages and/or lower effective maintenance doses, and/or reduced associated undesired or adverse effects in terms of frequency or severity of occurrence, or both. The present invention also relates to methods and materials for modulating a host humoral immune response, especially reducing, inhibiting, or preventing a host humoral immune response.