Peptidergic innervation of the Bursa Fabricii: interrelation with T-lymphocyte subsets

Expression of pituitary adenylate cyclase-activating polypeptide in the primary lymphoid organs of the duck Anas platyrhynchos

The expression of pituitary adenylate cyclase-activating polypeptide (PACAP) was studied in the thymus and bursa of Fabricius of the duck Anas platyrhynchos, at different ages, using immunohistochemistry, Western blotting, RT-PCR and sequencing. In the thymus, PACAP immunoreactivity (-ir) was found in lymphoid cells. CD68/ and PGP 9.5/PACAP38 double labelling showed that PACAP was not expressed either in macrophages or in epithelial cells, suggesting that the PACAP-positive cells observed were lymphoid cells. Immunoreactive lymphocytes were observed in the interlobular septa. They increased in number with ageing. In the bursa, PACAP-ir was found in nerve fibres and in a few lymphoid cells. RT-PCR revealed PACAP mRNA expression in the thymus but not in the bursa. These results suggest that PACAP plays a role in the functions of the immune system in birds.

Generation and phenotypic characterization of a galanin overexpressing mouse

In most parts of the peripheral nervous system galanin is expressed at very low levels. To further understand the functional role of galanin, a mouse overexpressing galanin under the platelet-derived growth factor-B was generated, and high levels of galanin expression were observed in several peripheral tissues and spinal cord. Thus, a large proportion of neurons in autonomic and sensory ganglia were galanin-positive, as were most spinal motor neurons. Strong galanin-like immunoreactivity was also seen in nerve terminals in the corresponding target tissues, including skin, blood vessels, sweat and salivary glands, motor end-plates and the gray matter of the spinal cord. In transgenic superior cervical ganglia around half of all neuron profiles expressed galanin mRNA but axotomy did not cause a further increase, even if mRNA levels were increased in individual neurons. In transgenic dorsal root ganglia galanin mRNA was detected in around two thirds of all neuron profiles, including large ones, and after axotomy the percentage of galanin neuron profiles was similar in overexpressing and wild type mice. Axotomy reduced the total number of DRG neurons less in overexpressing than in wild type mice, indicating a modest rescue effect. Aging by itself increased galanin expression in the superior cervical ganglion in wild type and transgenic mice, and in the latter also in preganglionic cholinergic neurons projecting to the superior cervical ganglion. Galanin overexpressing mice showed an attenuated plasma extravasation, an increased pain response in the formalin test, and changes in muscle physiology, but did not differ from wild type mice in sudomotor function. These findings suggest that overexpressed galanin in some tissues of these mice can be released and via a receptor-mediated action influence pathophysiological processes.

Age-related changes in the avian primary lymphoid organs (thymus and bursa of Fabricius)

The avian primary lymphoid organs, the thymus and the bursa of Fabricius, undergo age-dependent changes leading in some cases to the complete atrophy of the organ. Nevertheless, the timetable of the involutive process as well as the consequences in the structure and functionality of the organs vary largely in the time frame and structural changes among species. On the other hand, and in contrast with the large body of literature reporting the structural and functional changes in mammalian primary lymphoid organs, the age-dependent changes in avian thymus and bursa of Fabricius are scarce, fragmentary, and heterogeneous. This article reviews the current literature on this topic, and focuses primarily on the involution of the bursa of Fabricius.

Expression of dopamine receptors in immune organs and circulating immune cells

The existence of dopamine (DA) D1- and D2-like receptors in the rat and pigeon thymus and in human peripheral blood lymphocytes was investigated. The selective D1-like antagonist [3H]-SCH 23390 was used as a ligand of DA D1-like receptors (D1 and D5 sites). Pharmacological analysis suggests that binding of [3H]-SCH 23390 to sections of thymus and to human peripheral blood lymphocytes belongs mainly to the dopamine D5 receptor subtype. Light microscope autoradiography, performed in sections of rat and pigeon thymus, revealed that these receptors are located primarily in the cortical layer. DA D2-like receptors (D2, D3 and D4 sites) were studied in sections of rat thymus and in peripheral blood lymphocytes by using the putative DA D3 receptor agonist [3H]-7-OH-DPAT as a ligand. Both rat and pigeon thymus and human peripheral blood lymphocytes express a putative DA D3 receptor. These data are in agreement with recent molecular biology studies performed in human peripheral blood lymphocytes. The demonstration of different subtypes of DA receptors in a primary immune organ such as the thymus and in circulating immune cells supports the hypothesis of an involvement of DA in the control of immune function.

Muscarinic cholinergic receptor subtypes in the pigeon bursa of Fabricius: a radioligand binding and autoradiographic study

The pharmacological profile and the anatomical localisation of muscarinic cholinergic receptor subtypes were studied in the pigeon bursa of Fabricius, using radioligand binding and autoradiographic techniques with [3H]quinuclidinyl benzilate (QNB) as a ligand. [3H]QNB was specifically bound to sections of bursa of Fabricius. The binding was time-, temperature- and concentration-dependent. The dissociation constant was 0.31 +/- 0.02 nM, and the maximum density of binding sites averaged 38 +/- 2.5 fmol/mg protein. The pharmacological profile of [3H]QNB binding to sections of pigeon bursa of Fabricius was consistent with the labelling of M2, M3 and M4 muscarinic receptor subtypes. Light microscope autoradiography showed the localisation of [3H]QNB binding sites in the medulla, in follicular septa, in the cortico-medullary border and in lesser amounts in the cortical layer. The functional significance of these receptors should be clarified in future studies.

Dopamine D5 receptor expression is unchanged in peripheral blood lymphocytes in essential hypertension

The present study was designed to investigate possible changes in the expression of lymphocyte dopamine receptor in essential hypertension. The expression of dopamine D5 receptor was evaluated by radioligand binding techniques using [3H]-SCH 23390 as ligand. Plasma catecholamines, aldosterone levels and plasma renin activity were also measured. Eleven borderline hypertensive patients, 15 patient with the mild essential hypertension, 7 patients with moderate essential hypertension and 5 patients with severe essential hypertension were examined. Plasma catecholamine levels were assayed by high pressure liquid chromatography with electrochemical detection. Dopamine D5 receptor was measured by radioligand binding techniques. Plasma aldosterone levels and renin activity were determined by radio immunoassay. [3H]-SCH 23390 was specifically bound to human peripheral blood lymphocytes. The binding was time-, temperature- and concentration-dependent with a dissociation constant (Kd) value of 0.59 nM and a maximum density of binding sites (Bmax) of 223 pmol/10(6) cells. Dopamine competed with [3H]-SCH 23390 binding in the submicromolar range suggesting the labelling of a dopamine D5 receptor. No changes in the density of [3H]-SCH 23390 binding sites were observed in human peripheral blood lymphocytes between essential hypertensive patients and normotensive subjects. Also catecholamines, plasma renin activity and aldosterone levels were unchanged. In spite of the availability of a sensitive technique for measuring dopamine receptors in human peripheral lymphocytes, no change in their expression was noticeable in essential hypertension. This suggests that dopamine receptor analysis in essential hypertension is not a useful marker for investigating hypertension-dependent changes of the peripheral dopaminergic system.

Age-related changes of the noradrenergic and acetylcholinesterase reactive nerve fibres innervating the pigeon bursa of Fabricius

Age-dependent changes in the innervation of the pigeon (Columba livia, L.) bursa of Fabricius, from hatching to 120 days of age, were studied by fluorescence-histochemical and neurochemical methods for demonstrating noradrenergic and acetylcholinesterase (AChE)-reactive nerve fibres respectively. The distribution of both nerve fibre types was largely perivascular. Furthermore, a few isolated nerve fiber profiles were observed beneath the bursal epithelium, in the interfollicular septa and in the follicular cortex. No nerve fibre profiles reaching the medulla of the lymphoid follicles were observed. In addition to nerve fibres, AChE reactive neuron-like cells were encountered within the capsule and interfollicular septa. AChE reactivity was also found in dendritic-like cells localized in the cortical and cortico-medullary border. No changes in the density of perivascular noradrenergic innervation were noticeable during the ages studied, whereas the density of AChE-reactive fibres supplying vessels reached the adult pattern at 30 days, and then remained unvaried. The density of non-perivascular nerve fiber profiles, specially the AChE reactive type, increased until 30 days, remained unchanged until 75 days and then increased with aging (90-120 days). The interrelationship between the autonomic nervous system and the immune system is discussed.

Radioligand binding characterization of putative dopamine D3 receptor in human peripheral blood lymphocytes with [3H]7-OH-DPAT

The presence and the pharmacological profile of dopamine D3 receptor have been investigated in human peripheral blood lymphocytes using radioligand binding techniques and the selective dopamine D3 receptor agonist [3H]7-hydroxy-N,N-di-n-pro-pyl-2-aminotetralin ([3H]7-OH-DPAT) as a ligand. [3H]7-OH-DPAT binding to human peripheral blood lymphocytes was time-, temperature-, and concentration-dependent and of high affinity with a dissociation constant value (Kd) of 0.27 +/- 0.05 nM and a maximum binding density (Bmax) of 14.7 +/- 0.06 fmol/2 x 10(6) cells. Binding was also reversible. The rank order of potency of displacers of [3H]7-OH-DPAT binding to human peripheral blood lymphocytes resembled that found for dopamine D3 receptor in rat brain homogenates or in rat or human cell lines. Our findings, which are consistent with those of other authors performed with molecular biology techniques, suggest that human peripheral blood lymphocytes express dopamine D3 receptor. In the brain, dopamine D3 receptor probably mediates the anti-psychotic effect of neuroleptics. The availability of a rapid and reproducible technique for its assay may contribute to evaluate its status in brain disorders characterized by impaired dopaminergic neurotransmission.

Dopamine D5 receptors in human peripheral blood lymphocytes: a radioligand binding study

In the present study we have investigated, using radioligand binding techniques and the dopamine receptor antagonist [3H]SCH 23390 as a ligand, the existence of specific dopamine D1-like receptors in human peripheral blood lymphocytes. [3H]SCH 23390 binding to human peripheral blood lymphocytes was time-, temperature-, concentration-dependent and of high affinity with a dissociation constant value (Kd) of 0.58 +/- 0.05 nM and a maximum binding density (Bmax) of 11.02 +/- 0.3 fmol/5 x 10(6) cells. The binding was also reversible. Pharmacological analysis displacement curves of [3H]SCH 23390 binding with dopamine competing with the radioligand in the submicromolar range suggests that peripheral blood lymphocytes express dopamine D5 receptors rather than dopamine D1 receptors. These results, which are consistent with studies performed with molecular biology techniques, suggest that dopamine may modulate peripheral blood lymphocyte activity. Radioligand binding techniques, applied to lymphocyte receptor studies for their feasibility and flexibility may be used to investigate the possible relationship between the immune and dopaminergic systems. Moreover, they could be employed as a tool in Parkinson's disease, migraine, schizophrenia and hypertension research.

Neuropeptide Y is an inducible gene in the human immune system

This study reports on neuropeptide Y (NPY) mRNA expression in human peripheral blood mononuclear cells (PBMC) and lymphoid tissues. By reverse transcription polymerase chain reaction (RT-PCR) it is shown that activated human PBMC of normal blood donors expressed the NPY gene. The PCR products had the expected size and Northern blotting demonstrated the presence of the 0.8-kb NPY mRNA. To define the subpopulations of mononuclear cells expressing this neuropeptide, purified monocytes, B cells and T cells were stimulated with specific activators. Monocytes and in vitro matured macrophages expressed NPY mRNA in response to phorbol myristate acetate (PMA). B lymphocytes expressed NPY mRNA following stimulation with antibody to surface immunoglobulin and PMA. In order to analyze whether these cell types express NPY under physiological conditions in vivo, human bone marrow, tonsil and thymus were analyzed. In situ hybridization of bone marrow revealed a small number of cells containing high levels of NPY mRNA which was also detected in RNA extracts of human thymus and tonsil. In summary, NPY is an inducible gene in human lymphocytes and monocytes and it is expressed at sites where these cells are activated in vivo.