Granzyme B, a novel mediator of allergic inflammation: its induction and release in blood basophils and human asthma

Abstract

Histamine, leukotriene C4, IL-4, and IL-13 are major mediators of allergy and asthma. They are all formed by basophils and are released in particularly large quantities after stimulation with IL-3. Here we show that supernatants of activated mast cells or IL-3 qualitatively change the makeup of granules of human basophils by inducing de novo synthesis of granzyme B (GzmB), without induction of other granule proteins expressed by cytotoxic lymphocytes (granzyme A, perforin). This bioactivity of IL-3 is not shared by other cytokines known to regulate the function of basophils or lymphocytes. The IL-3 effect is restricted to basophil granulocytes as no constitutive or inducible expression of GzmB is detected in eosinophils or neutrophils. GzmB is induced within 6 to 24 hours, sorted into the granule compartment, and released by exocytosis upon IgE-dependent and -independent activation. In vitro, there is a close parallelism between GzmB, IL-13, and leukotriene C4 production. In vivo, granzyme B, but not the lymphoid granule marker granzyme A, is released 18 hours after allergen challenge of asthmatic patients in strong correlation with interleukin-13. Our study demonstrates an unexpected plasticity of the granule composition of mature basophils and suggests a role of granzyme B as a novel mediator of allergic diseases.

Death by a Thousand Cuts: Granzyme Pathways of Programmed Cell Death

“…During inflammation and infection, elevated levels of granzymes exist in both serum and other bodily fluids. Examples in which extracellular granzymes have been detected include the serum of patients undergoing acute cytomegalovirus infection or chronic HIV infection, the joints of rheumatoid arthritis patients, and the bronchoalveolar lavage fluid of allergen-challenged patients with asthma and patients with chronic obstructive pulmonary disease (9,114,(179)(180)(181)(182)(183). Elevated granzyme levels also occur in the serum of patients with endotoxemia and bacteremia, supporting the idea that granzymes are expressed and secreted by activated leukocytes, not just by lymphocytes (184).…”

“…Because the GzmB gene is encoded within a few hundred kilobases of mast cell proteases, the GzmB genomic region may be open and active in mast cells, allowing coordinated GzmB expression with mast cell chymase and tryptase. In human basophils, which are developmentally related to mast cells, IL-3-mediated GzmB induction in the absence of GzmA and perforin expression has also been reported (9). Expression of GzmB in mast cells and basophils suggests a role of GzmB in mediating allergic disease.…”

A quarter century of granzymes

“…90 Furthermore, it has become appreciated that GrB is expressed in the absence of perforin by a variety of non-lymphoid cells. [91][92][93] Thus, there is great speculation that GrB may have extracellular functions that promote extracellular matrix remodeling, cell death, and inflammation. In support of this theory, reports have demonstrated GrB-mediated proteolysis of extracellular matrix proteins.…”

Granzymes in cancer and immunity

“…For example, transformed and activated primary B cells, mast cells, keratinocytes, basophils, macrophages and blood polymorphonuclear neutrophils have all been shown to express granzyme B. 11,[14][15][16][17][18][19][20] Mast cells are especially abundant at the boundary between the internal environment and the outside world, for example, in the skin and lungs, and are thus perfectly situated to coordinate an immune response against a nascent infection. Granzyme B, but not granzyme A or perforin, is expressed by mast cells and secreted in an active form after ligation of the FceR1 receptor.…”

“…Coupled with observations that certain granzymes are expressed and secreted by B cells, mast cells, keratinocytes, basophils, as well as other cell types, in the absence of detectable perforin, this suggests that granzymes may have hitherto unsuspected roles in immunity. 11,[14][15][16][17][18][19][20] Thus, in addition to acting as cell death effector molecules on delivery to target cells, granzymes may also possess activity on release into the extracellular space ( Figure 1). The expanding role for granzymes as possible soluble mediators of inflammation will be discussed later in this review.…”