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A retrospective study was conducted at three centers to examine the participation of neutrophils and eosinophils in the inflammatory processes associated with atopic keratoconjunctivitis (AKC) and vernal keratoconjunctivitis (VKC).Conjunctival specimens were obtained from four patients with AKC, six with VKC, and five normal subjects. Indirect immunofluorescent staining was used to localize neutrophil elastase (NE) and eosinophil granule major basic protein (MBP) in serial sections of all specimens.Specimens from both AKC and VKC patients revealed extracellular deposition of NE and MBP. Control specimens showed no or minimal extracellular NE, and no MBP. Statistical analysis demonstrated significantly greater extracellular MBP deposition in AKC specimens compared to controls (p = 0.009), and VKC specimens showed significantly greater staining for both extracellular MBP (p = 0.005) and NE (p = 0.006).These results suggest that neutrophils, in addition to eosinophils, play an active role in the pathogenesis of AKC and VKC as evidenced by the extracellular deposition of their specific granule proteins.

The response of basophil cytosolic free Ca2+ concentrations ([Ca2+]i) to stimulation by eosinophil granule major basic protein (MBP) was assessed using digital video microscopy. MBP stimulated an elevation in basophil [Ca2+]i that, in general, developed slowly and increased monotonically. In some experiments, however, the average rise in [Ca2+]i was biphasic, with an initial transient increase followed by a larger and more sustained elevation. At the single cell level MBP stimulation caused frequent, asynchronous oscillations in [Ca2+]i that ranged up to 300 nM in amplitude. Chelation of extracellular Ca2+ selectively blocked the second, sustained rise in [Ca2+]i as well as MBP-induced histamine release. Within individual experiments, the increase in [Ca2+]i paralleled the level of histamine release. These results demonstrate that, unlike the activation of neutrophils or eosinophils, basophil activation by MBP correlates with an elevation in [Ca2+]i. Further, the MBP induced [Ca2+]i response exhibits several features in common with the IgE-mediated [Ca2+]i response.

The sera of all pregnant women contain increased amounts of a protein biochemically and immunologically similar to the eosinophil granule major basic protein (MBP). Immunofluorescence shows that the pregnancy-associated MBP is localized to placental trophoblastic cells. This information raises important questions about the function of pregnancy-associated MBP because of the potential biological functions attributed to its eosinophil counterpart (namely, its potent toxic and cytostimulatory activities). Previous studies demonstrated the presence of an immunologically cross-reactive protein in the placentae and plasma of pregnant non-human primates. Here, plasma MBP levels were measured throughout gestation in cynomolgus monkeys. In early pregnancy, only modest increases in MBP were found in contrast to the sharp rise observed in the first 20 weeks of human pregnancy. During the final one-third of gestation, striking increases in plasma MBP occurred in the monkeys. This parallels the late rise in MBP seen in humans in the third trimester. Thus, the cynomolgus monkey may serve as a model to clarify the role of the MBP in the biochemical events that culminate in parturition.

We have developed an indirect immunofluorescent method for detection of the guinea pig eosinophil granule major basic protein (MBP) in formalin-fixed, paraffinembedded tissues. The method is specific for MBP, permits MBP localization in cells and tissues, and eliminates eosinophil non-specific fluorescent staining.

We measured the levels of major basic protein and Charcot-Leyden crystal protein in tears from patients with ventral keratoconjunctivitis or miscellaneous inflammatory or noninflammatory ocular conditions, and from normal subjects. Patients with vernal keratoconjunctivitis had significantly increased levels of both proteins in their tears compared with the other subjects tested; levels of major basic protein seemed to correlate with the severity of the disease. The levels of Charcot-Leyden crystal protein paralleled those of major basic proteins.

Leukocytes of 22 individuals were incubated with a suboptimal concentration of eosinophil granule major basic protein and the amount of histamine release was determined. Cells from 20 of the 22 donors had a histamine release of greater than or equal to 15%. The use of selected donors on repeated occasions revealed significant variability in individual donor responsiveness. The findings support a role for major basic protein activation of human basophils in allergic reactions.