Enhancement of the immune response leading to protection against bacterial and fungal infections was shown using different schedules of immunization with microbial pigments and a polysaccharide. The group of mice given carotenoids of Rhodotorula glutinis (preparation I) and polysaccharide of Spitulina platensis (IV) survived for 2 weeks after Pseudomonas aeruginosa infection. The groups of mice given carotenoids (I), polysaccharide (IV), I+IV and with the crude phycocyanin of S. platensis (III)+IV survived for 2 weeks after Candida albicans infection. All other groups recorded a maximum level of mortality reaching 2 mice per group either after immunization or post-infection. Adding the carotenoids, phycocyanin and polysaccharides to food as additives might therefore enhance the human immune response against microbial infections.