Abstract
Microscopy of lymphoid organs was studied in the guinea pig at different developmental stages – fetus, pup, and adult. Liver is a lobed organ, coated with a mesothelium, and it consists of sinusoids and cell plates in its parenchyma, named hepatocytes. Thymus is covered by a thin capsule of connective tissue which is protruded as septa into the entire organ. The parenchyma of each lobule is not clearly separated into a cortex and medulla. Hassall’s corpuscles are abundant. Lymph nodes are arranged into cortex and medulla. The cortex has germinal centers or lymphoid nodules, surrounded by diffuse lymphoid tissue. Spleen is divided into red and white pulp. Trabeculae of connective tissue are protruded into the spleen from the capsule; however, they are sparsely found around the red and white pulps. Germinal centers were found in the white pulp, where small and large lymphocytes and lymphoblasts can be found. Since the guinea pig is regarded as an important model for morphological studies due to its closeness to human beings, this article raises relevant information on the structural components of the lymphoid system in these animals, providing a new source of data to other knowledge fields.
Highlights
Animal models are often used for pre-clinical testing of drugs and vaccines
This study aims to describe the microscopic features of lymphoid organs in the guinea pig, such as the spleen, thymus, lymph nodes, and liver, using individuals from different age groups
All animals were euthanized by anesthetic overdose with 50 mg/kg of ketamine (Ketamin-S®, Cristália) and 2 mg/kg of xylazine hydrochloride (Calmiun®, Union Agener); the necropsy was performed for collecting lymphoid organs, i.e. spleen, thymus, lymph nodes, and liver
Summary
Animal models are often used for pre-clinical testing of drugs and vaccines. In order to choose the right species to use in a particular study, its immune system has to be closely related to that of humans. The similarities enable a better understanding of human diseases and they are useful for developing drugs used in human medicine (MERCHANT et al, 2011). The main function of lymphoid organs is protecting the body against invading pathogens or antigens (bacteria, parasites, and viruses). The immune response occurs when the body detects the pathogen or antigen. Lymphoid cells, tissues, and organs have a wide distribution in the body. The major lymphoid organs are lymph nodes, tonsils, thymus, and spleen (EROSCHENKO, 2008)
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