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Morphological alterations in hemal nodes in splenectomized cattle

Modificações na morfologia dos nódulos hemolinfóides de bovinos esplenectomizados

Abstract

Pelo estudo das alterações morfológicas nos nódulos hemolinfóides, averiguou-se a compensação da deficiência imunológica transitória em bovinos esplenectomizados. Houve aumento acentuado de tamanho dos nódulos hemolinfóides dois meses após a esplenectomia. Além disso, ocorreu aumento significativo na espessura da zona intermediária dos nódulos hemolinfóides, bem como hiperplasia celular porém sem modificação na população e distribuição das células. As células B foram detectadas na zona central dos folículos, enquanto que as CD4+ se assentaram no córtex, na área interfolicular e nos cordões da zona intermediária. As células M2+ estavam dispersas no tecido cordonal e as CD8+ coraram-se de modo similar às células CD4+.

Cattle; hemal node; splenectomy; Bovino; nódulo hemolinfóide; esplenectomia


Cattle; hemal node; splenectomy; Bovino; nódulo hemolinfóide; esplenectomia

COMMUNICATION

(Comunicação)

Morphological alterations in hemal nodes in splenectomized cattle

(Modificações na morfologia dos nódulos hemolinfóides de bovinos esplenectomizados)

N. Bassan1, F. Vasquez2, M. Vinuesa1, P. Cerrutti2, S. Bernardi2

Recebido para publicação, após modificação, em 22 de março de 1999.

Colaboradores: S. Roma, F. Pérez

1Faculdad de Ciencias Médicas. – Universidad Nacional de Rosario

Santa Fe 3100 – Rosario – Argentina

2Faculdad de Ciencias Veterinarias – Universidad Nacional de Rosario - Argentina

Bovine hemal nodes are defined as lymphatic structures with blood circulation only. The distribution of these nodes is typically along the great vessels, mediastinic and mesenteric regions, perineal fat and subcutaneous tissue (Fagioli et al., 1981). They are ovoid shaped, dark red, exhibiting individual and racial variability regarding number and size (Cecarelli et al., 1981; Gargiulo et al., 1984). The nodes present a connective capsule mainly composed of collagen, elastic and reticular fibers, smooth muscle and abundant vessels (Holdsworth et al., 1990), with thin projections branching into the organ (Rovere et al., 1980; Parsons et al., 1989). From the capsule to the central region of the node three regions can be distinguished: 1-subcapsular, formed by the marginal sinus, 2-intermediate, contained lymphatic tissue (diffuse follicular and cord-like), blood sinuses and trabeculas and 3-central, mainly composed of vascular sinuses, trabeculas and cord-like lymphatic tissue (Folse et al., 1971; Ugalde et al., 1986).

Splenectomy carried out experimentally on animals or due to abdominal trauma in human beings induces immunosuppression, with different characteristics depending on the species and on the time after splenectomy (Lorvik et al., 1983; Aaberge et al., 1990; Demeter et al., 1990). Some authors described modifications in other lymphatic structures for compensating the transient immunologic deficiency after surgery (Fabian, 1981; Bergmann et al., 1990; Van Den Dobbelsteen, 1993). Furthermore, as bovine hemal nodes present some similarities with the structure of the spleen (Cecarelli et al., 1981), the aim of the present work is to describe macro and microscopic modifications in bovine hemal nodes after experimental splenectomy.

Twenty two-month-old British Aberdeen Angus calves were randomly divided into two groups of 10 animals each: 1- control group (CG) and 2- experimental group (EG). The animals were kept in pens and received water ad libitum and dry forage. Animals in the EG group were splenectomized. Two months later, the animals of both groups were killed and the mesenteric and retroperitoneal hemal and lymph nodes were removed along the major axis, and then divided into two categories: a- small, <0.99cm; and b- large, >1cm. The data are presented as mean and Student t test for unpaired data; correlation analysis was performed.

For microscopy, fragments of small and large hemal nodes and lymph nodes were fixed in 10% formaldehyde, parafin embedded and 6µm sections were stained with Masson's trichrome. Ten intermediate regions of control and experimental hemal nodes were measured by means of an eye piece grid.

For immunohistochemistry technique tissue fragments were immersed in OCT compound(Miles Scientific, UK), frozen in isopentane in liquid nitrogen and stored at –20ºC. Cryostat sections with 8mm in thickness were obtained and stored until used. The sections were incubated with the following monoclonal antibodies (VMRD Inc., USA) (mAbs): anti-bovine CD4 (CACT138A), CD8 (CACT80C), B5 (CH127A), M2 (CH137A) (Baldwin & Mac Hugh, 1988) and stained by alkaline phosphatase-anti alkaline phosphatase method (APAAP) (ZYMED, USA) (Rabinovsky & Tsu Ju, 1986).

The results showed an increase in hemal nodes from splenectomized animals due to intermediate zone thickness increase. No modifications in size and structure of lymph nodes were noted in experimental group.

The macroscopic measures are presented in Tab. 1 and micrometry results in Tab. 2.

Splenectomized animals showed a significant increase (P<0.01) in size in both, small and large hemal nodes compared to control ones (Tab. 1). The lymph nodes did not present size modifications.

The micrometry results showed a significant increase in diameter (P<0.01) of hemal nodes in the experimental group due to increase in the intermediate zone (Tab. 2) The marginal and deep zones did not show significant differences.

An increase in thickness of the intermediate zone due to an increase of numbers of cells was observed in the splenectomized group (Fig. 1 and 2). Despite this change, the localization of the specific cells, characterized by immunohistochemistry, was similar to that found in control animals. B cells were detected mainly in the central zone of follicles. CD4+ lymphocytes were observed in follicle cortex, interfollicular area, and in cords of intermediate zone (Fig. 3). Anti-CD8+ mAb had similar tinctorial features as anti-CD4+ mAb. Scattered M2+ cells were evident in chord-like lymphatic tissue (Fig. 4).



The fact that hemal nodes presented hypertrophy and hyperplasia in lymphatic tissue due to splenectomy and the absence of modifications in lymph nodes from splenectomized bovines, allows the conclusion that hemal nodes could be structures capable of performing a supplementary role in splenic function in young splenectomized cattle.

Keywords: Cattle, hemal node, splenectomy

RESUMO

Pelo estudo das alterações morfológicas nos nódulos hemolinfóides, averiguou-se a compensação da deficiência imunológica transitória em bovinos esplenectomizados. Houve aumento acentuado de tamanho dos nódulos hemolinfóides dois meses após a esplenectomia. Além disso, ocorreu aumento significativo na espessura da zona intermediária dos nódulos hemolinfóides, bem como hiperplasia celular porém sem modificação na população e distribuição das células. As células B foram detectadas na zona central dos folículos, enquanto que as CD4+ se assentaram no córtex, na área interfolicular e nos cordões da zona intermediária. As células M2+ estavam dispersas no tecido cordonal e as CD8+ coraram-se de modo similar às células CD4+.

Palavras-Chave: Bovino, nódulo hemolinfóide, esplenectomia

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Publication Dates

  • Publication in this collection
    05 Apr 2001
  • Date of issue
    Oct 1999

History

  • Received
    22 Mar 1999
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