Table 1.

Immune defects and associated pathogens in hematologic malignancies and HCT

Immune Impairment	Potential Causes	Spectrum of Respiratory Infections
Neutrophil number/function	Leukemia Lymphoma Myelodysplastic syndrome Cytoreductive therapies Corticosteroids Hematopoietic stem cell transplant	Gram-negative bacilli Gram-positive cocci Invasive molds (eg, Aspergillus spp, Mucorales, Fusarium, Scedosporium)
T lymphocytes	Lymphoma Corticosteroids T-cell depletion Drugs Calcineurin inhibitors Mammalian target of rapamycin inhibitors	Intracellular bacteria (eg, Nocardia, mycobacteria, legionella) Viruses (eg, respiratory viruses, latent Herpesviridae) Fungi (eg, Pneumocystis jirovecii, Cryptococcus spp, Histoplasma capsulatum, Coccidioides spp, Aspergillus spp, Micorales, Fusarium, Scedosporium) Parasites (eg, Strongyloides spp, Toxoplasma spp)
B lymphocytes and humoral immunity	Leukemia Multiple myeloma Anti–B-cell antibodies Splenectomy Plasmapheresis Drugs	Encapsulated bacterial (eg, Pneumococcus, H influenza) Mycoplasma spp