| 1992-1997 | Interim Head | University of Illinois at Chicago | Department of Microbiology and Immunology |
| 1991-present | Professor | University of Illinois at Chicago | Department of Microbiology and Immunology |
| 1990-1991 | Professor | University of Illinois at Chicago | Department of Biological Sciences |
| 1988-1990 | Associate Professor | University of Illinois at Chicago | Department of Microbiology and Immunology |
| 1986-1987 | Acting Director | University of Illinois at Chicago | Laboratory of Molecular Biology Department of Biological Sciences |
| 1986-1990 | Associate Professor | University of Illinois at Chicago | Department of Biological Sciences |
| 1979-1986 | Assistant Professor | University of Illinois at Chicago | Department of Biological Sciences |