Defense Date


Document Type


Degree Name

Doctor of Philosophy


Microbiology & Immunology

First Advisor

Thomas F. Huff


We have identified a late, committed stage in the differentiation of the mast cell progenitor just prior to granulation. This mast cell-committed progenitor (MCCP) differs from the more primitive bone marrow mast cell progenitor in that it is able to proliferate and differentiate in the absence of interleukin-3 (IL-3) when cultured on a monolayer of embryonic skin or 3T3 fibroblasts. The MCCP can be harvested from the mesenteric lymph nodes of mice in their fourteenth day of infection with the rodent hookworm Nippostrongylus brasiliensis and can be cloned in a methylcellulose culture system by supplementing the cultures with fibroblast-conditioned medium from monolayers of embryonic skin or 3T3 fibroblasts. The mesenteric lymph node was virtually uncontaminated with hematopoietic progenitors other than the MCCP.

The MCCP acquires a mucosa! mast cell phenotype when cloned in the presence of IL-3, but begins to take on a connective tissue mast cell phenotype when cloned in the presence of fibroblast conditioned medium. Upon fractionation by size exclusion chromatography, fibroblast conditioned medium contained a novel protein which supported proliferation of the MCCP and a separate granulation factor; thereby, proliferation and granulation can be uncoupled in vitro. These data demonstrate that IL-3 independent proliferation and differentiation of the MCCP does not require cell contact with fibroblasts. T cell-depleted cultures consistently produced higher numbers of mast cells than did nondepleted cultures. IL-3 production in the mesenteric lymph node peaked at day 11 and may instrumental in the transition of the IL-3 dependent progenitor into the MCCP.

When mast cell-deficient SI/SId or W/Wv mice were infected with Nippostrongylus, SI/SId mice, but not W/Wv' mice, produced the MCCP. To determine if these mice make the fibroblast derived factors that support development of the MCCP, monolayers were prepared from skin connective tissues of SI/SId and W/Wv mice, and MCCP from normal mice were cloned in the presence of conditioned medium from these monolayers. Fibroblast conditioned mediurn from monolayers prepared from W/Wv mice, but not SI/SId mice, was able to support the development of mast cell colonies from MCCP.


Scanned, with permission from the author, from the original print version, which resides in University Archives.


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