Interferons (IFNs) derived from WBCs (IFN-α- and IFN-γ) or from fibroblasts (IFN-β) or synthesized in bacteria by recombinant genetic techniques are glycoproteins that have antitumor and antiviral activity, which may originate partially from immunologically mediated mechanisms. Depending on the dosage, IFNs may either enhance or decrease cellular and humoral immune functions and may affect macrophage and NK cell activity. IFNs also inhibit division and certain synthetic processes in a variety of cells. Human clinical trials have indicated that IFNs have antitumor activity in hairy cell leukemia, chronic myelocytic leukemia, and AIDS-associated Kaposi’s sarcoma. Some responsiveness has been seen to a lesser degree in non-Hodgkin’s lymphoma, multiple myeloma, and ovarian carcinoma. However, IFNs are quite toxic; patients may develop fever, malaise, leukopenia, alopecia, and myalgia.

Bacterial adjuvants (eg, attenuated tubercle bacilli [BCG]), extracts of BCG (eg, methanol-extracted residue), or killed suspensions of Corynebacterium parvum have been used in randomized trials. They have been used with or without added tumor antigen to treat a broad variety of cancers, usually along with intensive chemotherapy or radiotherapy. Direct injection of BCG into melanoma nodules almost always leads to regression of the injected nodules and, occasionally, of distant, noninjected nodules. Intravesicular instillation of BCG in patients with superficial bladder carcinoma has prolonged disease-free intervals, possibly as a result of immunologic mechanisms. Some studies suggest that methanol-extracted residue may help prolong drug-induced remission in acute myeloblastic leukemia and that BCG added to combination chemotherapy may increase survival in patients with ovarian carcinoma and possibly with non-Hodgkin’s lymphoma. However, many studies have shown no benefit.