The investigators hypothesize that neutrophils and monocytes developed under the influence of Interferon- gamma-1b (IFN-γ-1b, Actimmune*) in vivo will display enhanced function across a broad range of activities related in large part to the transcriptional activation effects of this cytokine. The investigators will evaluate the effects of IFN-γ in healthy human subjects in vivo on gene expression, biologic activity markers, and functional activity of myeloid cells in single dose studies and in steady state studies.

Named for their potent ability to interfere and protect against viral infections, interferons (IFNs) have many regulatory effects on the immune system.1 Of the members of the two classes of these compounds, IFN-γ has the most diverse and powerful immune effects. Studies have mostly evaluated IFN-γ interactions with cells of adaptive immunity, including macrophages and lymphocytes. Effects on innate immunity, particularly polymorphonuclear leukocytes or neutrophils and monocytes are less well studied. However, investigations have suggested that IFN-γ may be involved in signal transduction, gene expression, the respiratory burst and neutrophil NADPH oxidase (Nox2) activity, phagocytosis, motility, microbicidal activity, and apoptosis. Not all of these functions are enhanced by IFN-γ; but the clinical use of this cytokine has been driven, in part by these results. For example, the primary motivation for initiating investigation of its beneficial clinical effects in Chronic Granulomatous Disease (CGD) was its effects on Nox2 activity.2 Most data in this area was based on studies using differentiated neutrophils from peripheral blood.1 However, the phenotype of neutrophils developed under the influence of this cytokine, not just changes expressed by exposure of differentiated cells to IFN-γ, is critical to understanding the physiologic effects of IFN-γ and the broad applications for its use in treatment of a range of human diseases. To expand their understanding of the role of IFN-γ in the development and functional integrity of the neutrophil, the investigators have completed a series of studies with PLB-985 cells in an in vitro culture system of myeloid cells. In this proposal, the investigators will evaluate innate immune activation and phagocyte function in healthy adult volunteers who are receiving IFN-γ.

Inclusion Criteria:

1. Healthy adults over the age of 18 years up to 60 years.
2. At time of screening subject is well and healthy;
3. Acute infections resolved;
4. Subject off treatment medications;
5. No diagnosis of chronic conditions or active health care issues for which the subject is actively followed by a health care provider or is on chronic medications.
6. Non-prescription medications for mild inter-current illnesses will be allowed at the discretion of the principal investigator.

Exclusion Criteria:

1. Pregnancy.
2. History of current infection;
3. Two weeks from most recent intercurrent infection;
4. History of recurrent infections or immunodeficiency.