A non-mammalian transfer factor, compositions including the non-mammalian transfer factor, and methods for generating and preparing the non-mammalian transfer factor. The non-mammalian transfer factor may have specificity for one or more antigens. A method of using the non-mammalian transfer factor includes administering either antigen-specific non-mammalian transfer factor or antigen non-specific non-mammalian transfer factor to mammals to treat or prevent pathogenic infections in the mammals.
