John J. Costa

Human eosinophils can express the cytokines tumor necrosis factor-alpha and macrophage inflammatory protein-1 alpha.

By in situ hybridization, 44-100% of the blood eosinophils from five patients with hypereosinophilia and four normal subjects exhibited intense hybridization signals for TNF-alpha mRNA. TNF-alpha protein was detectable by immunohistochemistry in blood eosinophils of hypereosinophilic subjects, and purified blood eosinophils from three atopic donors exhibited cycloheximide-inhibitable spontaneous release of TNF-alpha in vitro. Many blood eosinophils (39-91%) from hypereosinophilic donors exhibited intense labeling for macrophage inflammatory protein-1 alpha (MIP-1 alpha) mRNA, whereas eosinophils of normal donors demonstrated only weak or undetectable hybridization signals for MIP-1 alpha mRNA. Most tissue eosinophils infiltrating nasal polyps were strongly positive for both TNF-alpha and MIP-1 alpha mRNA. By Northern blot analysis, highly enriched blood eosinophils from a patient with the idiopathic hypereosinophilic syndrome exhibited differential expression of TNF-alpha and MIP-1 alpha mRNA. These findings indicate that human eosinophils represent a potential source of TNF-alpha and MIP-1 alpha, that levels of expression of mRNA for both cytokines are high in the blood eosinophils of hypereosinophilic donors and in eosinophils infiltrating nasal polyps, that the eosinophils of normal subjects express higher levels of TNF-alpha than MIP-1 alpha mRNA, and that eosinophils purified from the blood of atopic donors can release TNF-alpha in vitro.

Regulation of Mouse and Human Mast Cell Development, Survival and Function by Stem Cell Factor, the Ligand for the c-kit Receptor

Stem cell factor (SCF), the ligand for the receptor (SCFR) that is encoded by the c-kit proto-oncogene, has many important effects in mouse and human mast cell development, survival, and function. SCF can promote mast cell survival by suppressing apoptosis, induce mast cell hyperplasia in murine rodents, experimental primates and humans, directly induce SCFR-dependent mast cell mediator release, and significantly modulate the extent of mast cell activation by Fc epsilon RI-dependent mechanisms. These findings raise several clinical issues and, in some cases, point to potentially significant therapeutic opportunities.

Immortalization of mouse bone marrow-derived mast cells with Ad12-SV40 virus

Mast cells arise in cultures of murine bone marrow in medium supplemented with interleukin-3 (IL-3). In the present study, we report the development of long-term mast cell lines from murine bone-marrow-derived cultured mast cells (BMCMC) following inoculation with adenovirus 12-simian virus 40 (Ad12-SV40) hybrid virus. One culture of Ad12-SV40 immortalized BMCMC (designated as MCP-5) was selected for further analysis. These transformed cells appear similar in morphology and histochemistry to the primary BMCMC from which they are derived and did not shed infectious virus into the culture supernatants. In addition, these cells synthesize predominantly chondroitin sulfate proteoglycans and contain histamine which is released following a physiologic stimulus. Limiting-dilution single-cell cloning produced five independent mast cell lines (MCP-5.1 to MCP-5.5). Southern blot analysis of genomic DNA isolated from these single-cell clones demonstrates different patterns of viral integration in all the five clones. All clones retain responsiveness to an exogenous source of IL-3 for growth and proliferation. Each single-cell clone also demonstrates a unique pattern of cytokine gene expression in response to calcium ionophore A23187 and phorbol-12-myristate-13-acetate. This suggests that within a culture of BMCMC there are differences in cytokine gene expression that vary from one cell to another. The availability of immortalized mast cell lines derived from murine bone marrow which retain their growth factor responsiveness and the ability to respond to degranulating stimuli should facilitate future studies of mast cell biology.

Basophils and Mast Cells Basic Biology and Clinical Significance

Basophils and mast cells are thought to represent critical effector cells in IgEdependent host responses to parasites and allergie diseases, and may also have important functions in a variety of other immunological, pathological, and perhaps physiological processes. Ehrlich identified mast cells in human connective tissues on the basis of the metachromatic staining properties of their prominent cytoplasmic granules (Ehrlich, 1878). Metachromasia refers to the change in color of some basic dyes that occurs when they bind to certain highly charged molecules, including some of the constituents of mast cell cytoplasmic granules. Ehrlich also described the basophil, a circulating leukocyte that contains cytoplasmic granules with staining properties similar to those of the mast cell (Ehrlich, 1879). Mast cells and basophils share several notable features besides staining properties (summarized in Table I). Both cell types are derived from bone marrow progenitor cells and both mast cells and basophils represent a major source of histamine and other potent chemical mediators which have been implicated in a wide variety of inflammatory and immunologie processes, including allergie disorders with components of immediate hypersensitivity (reviewed in Galli and Lichtenstein, 1988; Holgate et al., 1993; Metcalfe et al., 1981; Schwartz and Huff, 1993; Galli, 1990, 1993). All in all mammalian species yet analyzed, both mast cells and basophils express plasma membrane receptors (FceRI) that specifically bind, with high affinity, the Fc portion of IgE antibody (Beaven and Metzger,, 1993; Kinet, 1990; Ishizaka, 1988; Benhamou and Siraganian, 1992).