Merkel's Home Page
Glenn J. Merkel, Ph.D.
Department of Microbiology & Immunology
Indiana University School of Medicine
Fort Wayne, IN  46805

The view from our lab (We wish!)

Our research focuses on studies with pathogenic fungi and bacteria. We are currently investigating the interactions of Cryptococcus neoformans with mammalian target cells. C. neoformans is an encapsulated yeast that causes life threatening infections in immunocompromised patients. Click HERE for photomicrographs.

Our previous work has demonstrated that C. neoformans specifically adheres to and is internalized by potential target cells such as the mouse lung epithelial cell below. What is shown is an electron micrograph of a section of a lung cell containing a number of internalized yeasts. (Merkel & Cunningham, 1992, J. Vet. Med. Mycol. 30, 115-121)

We have recently demonstrated that C. neoformans adheres to and is internalized by a human lung epithelial cell line.
(Merkel, G.J. & B. Scofield. 1997. The in vitro interaction of Cryptococcus neoformans with human lung epithelial cells. FEMS Immunol. Med. Microbiol. 19: 203-213.)
Click to view the abstract.

Using this same human lung epithelial cell line we have recently demonstrated that antigens secreted by C. neoformans inhibit tumor necrosis factor-induced intercellular adhesion molecule-1 expression on these epithelial cells.
(Merkel, Glenn J. and Barbara A. Scofield. 2000. The effects of Cryptococcus neoformans secreted antigens on tumor necrosis factor induced intercellular adhesion molecule-1 expression on human lung epithelial cells. FEMS Immunol. Med. Microbiol. 29: 329-332.) Click to view the abstract.

Another recent paper characterizes a monoclonal antibody to those secreted antigens above that inhibit TNF-induced ICAM-1 expression. (Merkel, G.J. & B.A. Scofield. 1999. An opsonizing monoclonal antibody recognizing a non-capsular epitope expressed on Cryptococcus neoformans. Infection & Immunity 67: 4994-5000.) Click here to view the abstract.
This monoclonal antibody (mAb) is interesting because it is the first one described that reacts with a secreted, non-capsular epitope and also opsonizes the yeasts making them more readily phagocytized. The attached micrographs show mouse phagocytes (click to view) and yeasts in the absence and presence of the mAb. Note few yeasts (highly refractile) are bound/phagocytized without the mAb. With the mAb, however, there is a substantial increase in the extent of phagocytosis. Immune electron microscopy (below) shows that the epitope that this mAb binds can be seen in the cell wall and in clusters at the membrane-wall interface (black gold particles show where the mAb has bound).

Click HERE to see a complete image.

We're also doing some interesting work with a monoclonal antibody that recognizes an epitope in bacterial peptidoglycan. (Merkel, G.J. and B.A. Scofield.2001. Characterization of a monoclonal antibody that binds to an epitope on soluble bacterial peptidoglycan fragments. Clin. Diag. Lab. Immunol. 8: 647-651.) Click here to view the abstract. We are currently engaged in animal studies to determine if anti-peptidoglycan antibodies can be used in an ELISA to diagnose bacteremia.

Most recently we've begun to study the interaction of Staphylococcus epidermidis and S. aureus with human umbilical vein endothelial cells, microvascular endothelial cells, and lung epithelial cells in culture. Our most recent publication (Merkel & Scofield. 2001. Interaction of Staphylococcus epidermidis with endothelial cells in vitro. Med. Microbiol. Immunol. 189:217-223) is the first demonstration of heat-induced adherence and internalization of S. epidermidis by human endothelial cells. Click HERE to see electron micrographs of S. epidermidis adhering to and invading endothelial cells. Most of our investigations now involve studies with Staphylococcus and microvascular endothelial cells since the microvasculature is probably the route that staphylococci use to disseminate from the blood into various tissues.

Click here for an old picture of me at work.

Merkel's Curriculum Vitae

“Ode to Candida"(the yeast)
by Glenn Merkel
(written around 1983)

  First Year Medical Students: Click HERE for information about Medical Microbiology and Immunology (Spring 2006).
 Click to view the statewide Immunology and Microbiology cores (PDF files).

  Second Year Medical Students: Click HERE for information about General Pathology (Fall 2005). All handouts are available at the Angel Website:


 American Society for Microbiology
 Centers for Disease Control and Prevention
 Infectious Diseases Society of America
Indiana College Network 
 Indiana University School of Medicine - Fort Wayne Center
Indiana Branch Home Page 
 Dept. Microbiology & Immunology, I.U. Sch. Med. 

 (Last modified November 9, 2005)