Human lymphocyte-eosinophil interactions. I. Modulation of phytohemagglutinin-induced lymphocyte proliferation by eosinophils

Effect of eosinophil-degranulating estrogens on spleen eosinophils and white pulp/red pulp ratio

A role for eosinophils in the immune reaction has not been yet established. Considering that these leukocytes accumulate in lymphoid organs under glucocorticoid stimulation, we explored the possibility that they participate in the depression of immune reactions induced by these hormones and that they degranulate to exert this action. In this context, we investigated the dose effect of three estrogens on the number and degranulation of spleen red pulp eosinophils and on the percentage of spleen cross sectional area comprising white pulp. Estradiol-17 beta or 4 (OH) estradiol-17 beta increased red pulp eosinophils at low doses: 2 (OH) estradiol-17 beta increased them at a very high dose. The three estrogens degranulated the spleen eosinophils and decreased the lymphocyte containing spleen white pulp. We propose that the decrease in white pulp is a response mediated by agents released from degranulating eosinophils under the action of estrogen. Consequently, both estrogen-induced eosinophil degranulation and estrogen-induced increase in red pulp eosinophil numbers are conditions contributing to a decrease in white pulp volume. All above evidence supports the hypothesis that eosinophils are involved in immunoregulation by diminishing the number of lymphocytes contained in lymphoid organs.

An improved method for the isolation of enriched canine peripheral blood mononuclear cell and peripheral blood lymphocyte preparations

A two-step purification method was developed for obtaining (1) peripheral blood mononuclear cell preparations of greater than 97% purity and (2) peripheral blood lymphocyte preparations of greater than 95% purity from canine whole blood with yields similar to or greater than those obtained by conventional techniques.

Phosphorylation and dephosphorylation of soluble proteins in human eosinophils

The effect of phorbol 12-myristate 13-acetate (PMA), calcium ionophore (A23187), opsonized zymosan (OZ), and N-formylmethionyl-leucyl-phenylalanine (f-Met-Leu-Phe) on protein phosphorylation was examined in purified eosinophils (eos) isolated from human peripheral blood. Eos were prelabeled with [32P]orthophosphate, stimulated with several activating agents for varying periods of time. The soluble proteins were then analyzed by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. In resting eos, there was phosphorylation of endogenous soluble proteins with molecular weights of 12, 16, 21, 40, and 66 kilodaltons (kDa). PMA, a potent activator of oxidative metabolism, induced phosphorylation of 19-, 40-, and 67-kDa proteins. A23187, a strong degranulating stimulus, caused phosphorylation of 40-, 53-, and 67-kDa proteins. OZ, a relatively weak stimulus for eos function, caused phosphorylation of 30-34-, 59-, 67-, and 93-kDa proteins. In addition, all the above stimuli caused a time-dependent dephosphorylation of 21-kDa protein. In contrast, f-Met-Leu-Phe caused neither phosphorylation of new proteins nor dephosphorylation of preexisting eos proteins. These findings demonstrate that selected stimuli affect phosphorylation of soluble eos protein. These results also suggest that phosphorylation of specific proteins in eos is an intermediary step in external stimulus-induced cell activation, which may involve many different cell functions.

Activated human eosinophils synthesize new proteins

In order to study the biochemical consequences of prolonged in vitro activation of human blood eosinophils, aqueous whole cell lysates, cell-free supernatants from resting eosinophils, and cells activated with opsonized zymosan, calcium ionophore (A23187), N-formylmethionylleucylphenylalanine (fMet-Leu-Phe), and phorbol 12-myristate 13-acetate (PMA) were analyzed by polyacrylamide gel electrophoresis (PAGE). In comparison to resting eosinophils, opsonized zymosan-activated eosinophil extracts demonstrated altered protein composition on both the native PAGE and sodium dodecyl sulfate (SDS) -PAGE. Three new polypeptides of apparent molecular mass 24 kDa, 43 kDa and 60 kDa appeared on SDS-PAGE gels when opsonized zymosan-activated eosinophil extracts were electrophoresed. In contrast, extracts from fMet-Leu-Phe, A23187, and PMA-activated eosinophils demonstrated neither altered polypeptide composition nor new polypeptides. Opsonized zymosan also induced the incorporation of L-[35S]methionine into eosinophil proteins and this was completely blocked by pretreating the cells with cycloheximide. This finding suggests that eosinophils activated by certain stimuli synthesize new proteins. These newly synthesized proteins, which are freely secreted into the medium during cell activation, may possess important immunological functions.

Effects of glucocorticoids on eosinophil colony growth

The in vivo and in vitro effects of glucocorticoids on eosinophilopoiesis were examined with soft agar cultures of bone marrow and peripheral blood cells. Prednisone, 10 mg four times daily for three days, administered to normal volunteers, caused a significant drop in circulating eosinophil numbers (p less than 0.005) but did not decrease eosinophil colony numbers in cultures of bone marrow or peripheral blood. A patient with peripheral blood eosinophilia demonstrated a larger percentage decrease in mean eosinophil colony numbers (50%) after prednisone than did any normal volunteer. Incubation of bone marrow cells for 1 hour with either high concentrations of hydrocortisone, up to 3.3 X 10(-4) mol/L, or with postinfusion plasma from volunteers administered intravenous hydrocortisone, plasma levels to 1.6 X 10(-5) mol/L, did not decrease the numbers of eosinophil colonies. At a concentration of 3.3 X 10(-6) mol/L of hydrocortisone, there was a slight but statistically significant stimulation of eosinophil colony numbers. In contrast, incubation with high concentrations of dexamethasone, 3.3 X 10(-4) mol/L or 3.3 X 10(-6) mol/L, significantly reduced eosinophil colony numbers. Prednisone caused a significant reduction in plasma levels of Charcot-Leyden crystal protein but not of eosinophil granule major basic protein. The results indicate that soft agar assay of eosinophil colony growth by blood or bone marrow cells cannot be used to model the in vivo eosinopenic effect of glucocorticoids, levels of dexamethasone in excess of levels commonly administered in clinical practice are required to inhibit eosinophilopoiesis in vitro, and patients with peripheral blood eosinophilia may be more susceptible to the eosinopenic effects of glucocorticoids than normal subjects.

Human eosinophil heterogeneity

The aim of this review is to examine some of the most important findings pointing toward human eosinophil heterogeneity. Special importance is given to cell density, surface receptors, metabolism and response to biological products or synthetic compounds.