Transfer factors are a complex group of more than 200 highly polar, hydrophilic, low molecular weight (less than 12,000 Daltons) proteins produced in small quantities by lymphoid cells (1). Their precise molecular structure has not been determined. They carry with them the parent lymphocyte's delayed-type hypersensitivity and cell-mediated immunity and pass it along to non-immune recipients, and appear to function across species. Transfer factors can be extracted from human or animal white blood cells, cloned lymphocytes grown in vitro, colostrum, and egg yolk. They appear to be well tolerated and in clinical settings have shown some signs of efficacy in treatment of herpes (2), acute infection in children (3), chronic fatigue syndrome (4), and Candidiasis (5). One study showed effectiveness in increasing white blood cells, CD8 lymphocytes and interleukin 2 levels among patients with HIV (6). Transfer factors are ineffective in treating hepatitis (7), multiple sclerosis (8), extrinsic bronchial asthma (9), human warts (10), juvenile rheumatoid arthritis (29), and acne vulgaris (11).
Studies have shown transfer factors ineffective in treating malignant melanoma (12), nasopharyngeal carcinoma (13), bronchogenic carcinoma (14), Hodgkin's disease (15), osteogenic sarcoma (16), and mycosis fungoides (17). In rats, transfer factors were shown to reduce tumor size and increase peripheral blood T-lymphocyte counts (21). Transfer factors show signs of effectiveness in increasing survival rates among patients with Stage I adenocarcinoma of the lung (18) and Stage I cervical cancer (19), but further research is warranted. In a study of children with leukemia, immunization with transfer factors conferred protection against varicella-zoster infection (20).
Overall, there is a paucity of large randomized controlled clinical trials, and a need for further research into the effectiveness of transfer factors.