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Bearing in mind the role of somatostatin in thymus functions, and changes of somatostatin level and expression of its receptors during postnatal life, the aim of this study was to investigate whether centrally applied SRIH-14 induces different changes in the thymic compartments and thymocyte profile in peripubertal and young adult rats. To this end, 4- and 10-week-old male AO rats were cannulated and treated intracerebroventriculary with three doses of SRIH-14, applied every other day. In peripubertal rats, SRIH-14 decreases thymic relative weight and volume, as well as the volume of thymic compartments, especially of deep cortex, as a result of thymocytes loss by apoptosis. Also, SRIH-14 increases the percentage of immature thymocytes preceding the DPTCRαβlow cells (DNTCRαβ-/low, DPTCRαβ-, SPCD8TCRαβ-/low and SPCD4TCRαβ-/low), decreases the percentages of DPTCRαβlow and DPTCRαβhi cells, while the relative proportion of CD4+/CD8+TCRαβhi cells remained unaltered. In young adult rats, SRIH-14 does not lead to changes in relative thymus weight, although decreases the thymic cortex cellularity and volume. In addition, decreases the percentage of DPTCRαβ-/hi cells and increases the percentages of cells within DNTCRαβhi and both SP subpopulations, but much more of the CD8+TCRαβhi subset. These results suggest that the effects of SRIH-14 on the thymus and thymocytes subpopulations are age-dependent. Sa obzirom da literaturni podaci ukazuju da somatostatin ima uticaja na funkciju timusa, kao i da se tokom postnatalnog života menja nivo somatostatina i ekspresija njegovih receptora u timusu, cilj ovog rada je bio da se ispita da li SRIH- 14 davan intracerebroventrikularno u prepubertalnih i mladih odraslih pacova, dovodi do različitih promena u zonama timusa i profilu timocitnih subsetova. Mužjacima pacova AO soja, starim 4 i 10 nedelja, ugrađene su kanile u treću moždanu komoru i oni su tretirani somatostatinom, ukupno tri doze, ubrizgane svakog drugog dana. U prepubertalnih pacova tretman somatostatinom dovodi do smanjenja relativne mase i zapremine timusa, kao i zapremine timusnih zona, naročito dubokog korteksa, što je bila posledica gubitka timocita apoptozom. Takođe, SRIH-14 je doveo do povećanja procenta timocita nezrelog fenotipa (DNTCRαβ-/low, DPTCRαβ-, SPCD8TCRαβ-/low i SPCD4TCRαβ-/low) prekusora DPTCRαβlow subpopulacije, smanjenja procenta DPTCRαβlow i DPTCRαβhi subsetova, dok je relativni odnos najzrelijih CD4TCRαβhi i CD8TCRαβhi timocita ostao neizmenjen. U mladih adulta primena somatostatina, iako dovodi do smanjena zapremine i celularosti korteksa ne dovodi do promena u relativnoj masi timusa. Procenat DPTCRαβ-/hi timocita je bio smanjen, dok je procentualno učešće DNTCRαβhi timocita i obe jednostruko pozitivne subpopulacije (CD4TCRαβhi i CD8TCRαβhi, više CD8TCRαβhi) u ukupnom broju timocita bilo povećano. Navedeni rezultati ukazuju da SRIH-14 različito utiče na morfologiju timusa i na subpopulacije timocita pacova u zavisnosti od uzrasta tretiranih životinja.

The present study was undertaken to reassess the recently challenged role of ovarian hormones in age-associated thymic involution. For this purpose, in eleven-month-old peripubertally ovariectomized (Ox) rats we analyzed: i) thymic weight and cellularity, ii) size of CD4+CD8+ double-positive (DP) thymocyte population, which is believed to correlate to the thymic capacity to export mature T cells, iii) number of recent thymic emigrants (RTEs), and iv) number of peripheral blood CD4+ and CD8+ lymphocytes. It was found that both thymic weight and cellularity were greater in Ox than in control rats. In addition, in Ox rats the numbers of DP thymocytes and both CD4+ and CD8+ RTEs, were significantly greater than in controls, indicating a more efficient generation of T cells in these rats. Furthermore, these findings, coupled with data indicating that the number of neither CD4+ nor CD8+ peripheral blood lymphocytes was affected by ovariectomy, most likely, suggest a reduced homeostatic proliferation of memory cells in Ox rats, i.e. broadening of TCR peripheral repertoire without changes in the overall number of T cells leading to a more efficient response to newly encountered antigens. The results indicate that the ovarian steroid deprivation from early peripubertal period leads to a long lasting postponement/alleviation of age-associated decline in T-cell mediated immune response. Ova istraživanja su preduzeta sa ciljem da se preispita uloga gonadnih hormona u involuciji timusa, koja je nedavno dovedena u pitanje. U tom cilju je kod 11 meseci starih ženki pacova, koje su ovarijektomisane (Ox) u peripubertetnom uzrastu, analizirana: i) težina i celularnost timusa, ii) broj CD4+CD8+ dvostruko pozitivnih (DP) timocita, za koji se smatra da odražavaju sposobnost organa da generiše zrele T limfocite, iii) broj neposrednih emigranata iz timusa (RTE) i iv) ukupan broj CD4+ i CD8+ limfocita u perifernoj krvi. Dokazano je da su težina i celularnost timusa bile značajno veće u Ox životinja. Kod ovih životinja je nađen i povećan broj DP timocita, kao i CD4+ i CD8+ RTE, što ukazuje na efikasniju produkciju T ćelija u njihovom timusu. Ovaj nalaz, u kontekstu nepromenjenog broja CD4+ i CD8+ ćelija u perifernoj krvi, takođe sugeriše smanjenu homeostatsku proliferaciju memorijskih ćelija, odnosno ukazuje na kvalitativne promene u perifernom T ćelijskom repertoaru (koje obezbeđuju efikasniji odgovor na nove antigene) bez kvantitativnih promena. U celini, rezultati ukazuju da u odsustvu hormona ovarijuma počevši od ranog peripubertetnog uzrasta dolazi do značajnog odlaganja/ublažavanja involucije timusa i posledičnih promena na periferiji.

The aim of this study was to investigate histomorphometrical characteristics of the thymus, bursa of Fabricius and spleen in the chickens vaccinated with a vaccine against Marek’s disease. For this purpose, we used newly hatched chickens of the light hybrid line, obtained from a local hatchery. The chickens were vaccinated on the 5th day after hatching with a bivalent cell-associated Marek's disease vaccine (PFU-2000 per dose). On day 13 both vaccinated chickens and unvaccinated controls were sacrificed, and thymus, bursa and spleen were removed and processed for light microscopy. The serial tissue sections, hematoxylin-eosine stained, were used for histomorphometric analysis. Vaccination against Marek’s disease decreased the relative mass of the lymphoid organs, and caused significant damage of the thymus and spleen in experimental chicken. In addition, vaccination, similar to Marek's disease virus, induced morphometric changes in the lymphoid organs. Namely, it significantly decreased the diameter and volume of lymphoid follicles, volume of follicular medulla and number of cells in the follicular cortex in the bursa of Fabricius. In the thymus, vaccination reduced the thymus volume and the absolute number of thymocytes. However, vaccination against Marek’s disease caused an increase in the diameter, number and volume of lymphoid follicles in the spleen. The present data suggest that vaccination against Marek’s disease was able to induce the immune response in processed organs, although it reduced the mass and number of lymphocytes in the major lymphoid organs.

To investigate the differences between thymocytes development in vivo and in vitro, thymus lobe fragments from 12-weeks old male Albino Oxford rats were cultivated over a 7-days period. In the controls and cultivated thymic lobes fragments were evaluated and the viability, apoptosis and cell cycle of thymocytes, as well as the histological characteristics of thymic tissue. Additionally, we analyzed the expression of CD4, CD8 and TCRαβ on thymocytes by flow cytometry. The obtained results showed that thymus cellularity decreased during cultivated time due to expanded apoptosis, decreased proliferation and the absence of progenitors reseeding thymus. The relative proportion of thymocyte subsets in the first 24 hours of culture remained similar as in the control. However, cultivation for 3 and 7 days modulated the relative proportions between thymoctye subsets. The percentage of DP TCRαβlow increased, DP TCRαβhi subset remained unchanged, both SP TCRαβhi subsets decreased while the same mature SP phenotype dominated in culture media. These results demonstrate that cultivated thymic fragments retain the capacity for T cell development, although cultivation modulates this process. Sa namerom da ispitamo razlike između in vivo i in vitro sazrevanja timocita gajili smo fragmente lobusa timusa poreklom od mužjaka Albino Oksford pacova, starih dvanaest nedelja, u vremenskom periodu od sedam dana. Nakon kultivacije određivani su vijabilnost, apoptoza i ćelijski ciklus timocita, kao i histološke osobine timusnog tkiva. Takođe je analizirano ispoljavanje markera diferentovanja CD4, CD8 and TCRαβ na površini timocita metodom tečne citofluorometrije. Dobijeni rezultati su ukazali da sedmodnevna kultivacija dovodi do smanjenja broja ćelija u timusu usled povećane apoptoze, smanjene proliferacije i odsustva ulaska progenitora timocita. Tokom prvih 24 sata kultivacije ne dolazi do promena u odnosima timocitnih populacija. Međutim, duže vreme kultivacije - 3 i 7 dana moduliše relativne odnose između timocitnih subpopulacija - povećava se procenat DP TCRαβlow, procenat DP TCRαβhi timocita ostaje nepromenjen, dok su procenti ćelija oba subseta SP TCRαβhi smanjeni, mada je prisustvo pomenutih SP subsetova dominantno u medijumu za kultivaciju. Navedeni rezultati pokazuju da kultivisani fragmenti timusnog tkiva zadržavaju sposobnost da podrže sazrevanje timocita u jednostruko pozitivne T ćelije, mada je diferentovanje timocita donekle modulisano kultivacijom.