Figure 1.

Effect of interleukin (IL)–7 on clinical and immunologic variables in critically ill coronavirus disease 2019 patient. A, A test dose of IL-7 (3 μg/kg) was administered followed by three additional doses of 10 μg/kg as indicated by red arrows. IL-7 increased the absolute lymphocyte count (ALC) from ~400 lymphocytes/μL to over 5,000 lymphocytes/μL. Green lines indicate upper and lower limit of normal for ALC; IL-7 was well tolerated and did not show any evidence of worsening lung inflammation as indicated by observing a decreasing Fio₂ (B) and improving oxygen saturation (C). Blue arrows in (B) and (C) indicate day of intubation and extubation. Immunologic function of patient immune effector cells was tested by enzyme-linked immunospot (ELISpot). T-cell interferon (IFN)–γ production was tested in peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3/CD28 before and after IL-7 therapy administration to the patient. 2.5 × 10⁴ PBMCs are plated for T-cell functional assay. Note the dramatic increase in the number of lymphocytes that produce IFN-γ (as represented by number of spot forming units [SFUs]) in upper row after IL-7 therapy (D, top row); severe acute respiratory syndrome coronavirus 2 spike, and nucleocapsid peptide antigens were incubated overnight in patient PBMCs before and after IL-7 therapy. 1 × 10⁵ PBMCs are plated to assess antigen-specific T cells. Note the dramatic increase in the number of IFN-γ–producing lymphocytes (SFU) reacting specifically to the viral antigens after IL-7 (D, second row); innate immune function was tested by ELISpot assay for tumor necrosis factor (TNF)–α in PBMCs stimulated with lipopolysaccharide (LPS). 2.5 × 10³ PBMCs are plated to assess innate immune function. Note the marked increase in the number of TNF-α–producing cells (SFU) after IL-7 (E). CD = cluster of differentiation, Spo₂ = oxygen saturation, NCAP = nucleocapsid protein.