CD3 IMMUNODEFICIENCIES

Asthma and pregnancy

Asthma complicates 4-8% of pregnancies. Mild and well-controlled moderate asthma can be associated with excellent maternal and perinatal pregnancy outcomes. Severe and poorly controlled asthma may be associated with increased prematurity, need for cesarean delivery, preeclampsia, growth restriction, other perinatal complications, as well as maternal morbidity and mortality. Optimal management of asthma during pregnancy includes objective monitoring of lung function, avoiding or controlling asthma triggers, patient education, and individualized pharmacologic therapy. Those with persistent asthma should be monitored by peak expiratory flow rate, spirometry to measure the forced expiratory volume in 1 second, or both. Step-care therapeutic approach uses the least amount of drug intervention necessary to control a patient's severity of asthma. Inhaled corticosteroids are the preferred treatment for the management of all levels of persistent asthma during pregnancy. It is safer for pregnant women with asthma to be treated with asthma medications than it is for them to have asthma symptoms and exacerbations. The ultimate goal of asthma therapy is maintaining adequate oxygenation of the fetus by prevention of hypoxic episodes in the mother. Asthma exacerbations should be aggressively managed, with a goal of alleviating asthma symptoms and attaining peak expiratory flow rate or forced expiratory volume in 1 second of 70% predicted or more. Pregnancies complicated by moderate or severe asthma may benefit from ultrasound for fetal growth and accurate dating and antenatal assessment of fetal well-being. Asthma medications should be continued during labor, and parturients should be encouraged to breastfeed.

Toward gene therapy for human CD3 deficiencies

The CD3 subunits of the T cell receptor-CD3 complex (TCR-CD3) help to regulate surface TCR-CD3 expression, and participate in signal transduction leading to intrathymic selection and peripheral antigen recognition by T lymphocytes. Humans who lack individual CD3 chains show impairments in the expression and activation-induced downregulation of TCR-CD3, and the defective immune responses that result may be lethal. We have investigated delivery of a normal CD3 chain to treat disorders of this type. Retroviral transduction of CD3gamma into CD3gamma-deficient peripheral blood T lymphocytes from two unrelated patients selectively corrected the observed TCR-CD3 expression and downregulation defects, but unexpectedly seemed to cause adverse effects that can be explained by an autoreactive recognition mechanism. These data support the feasibility of gene therapy for human CD3 deficiencies, but also suggest that gene transfer into postthymic lymphocytes carrying mutations on T cell recognition or activation pathways may disrupt their intrathymic calibration and become harmful to the host.

TCR dynamics in human mature T lymphocytes lacking CD3 gamma

The contribution of CD3gamma to the surface expression, internalization, and intracellular trafficking of the TCR/CD3 complex (TCR) has not been completely defined. However, CD3gamma is believed to be crucial for constitutive as well as for phorbol ester-induced internalization. We have explored TCR dynamics in resting and stimulated mature T lymphocytes derived from two unrelated human congenital CD3gamma-deficient (gamma(-)) individuals. In contrast to gamma(-) mutants of the human T cell line Jurkat, which were selected for their lack of membrane TCR and are therefore constitutively surface TCR negative, these natural gamma(-) T cells constitutively expressed surface TCR, mainly through biosynthesis of new chains other than CD3gamma. However, surface (but not intracellular) TCR expression in these cells was less than wild-type cells, and normal surface expression was clearly CD3gamma-dependent, as it was restored by retroviral transduction of CD3gamma. The reduced surface TCR expression was likely caused by an impaired assembly or membrane transport step during recycling, whereas constitutive internalization and degradation were apparently normal. Ab binding to the mutant TCR, but not phorbol ester treatment, caused its down-modulation from the cell surface, albeit at a slower rate than in normal controls. Kinetic confocal analysis indicated that early ligand-induced endocytosis was impaired. After its complete down-modulation, TCR re-expression was also delayed. The results suggest that CD3gamma contributes to, but is not absolutely required for, the regulation of TCR trafficking in resting and Ag-stimulated mature T lymphocytes. The results also indicate that TCR internalization is regulated differently in each case.