Thymus‐dependent lymphoid regions in the spleen of the lizard, <i>Calotes versicolor</i>

Pitchappan, R. M.; Muthukkaruppan, Veerappan

doi:10.1002/jez.1401990203

Cited by 17 publications

(3 citation statements)

References 20 publications

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“…In contrast, the lymphocyte compartment of the reptilian PALS is presumed to be dominated by T cells; the PALS cells have the characteristic morphology of lymphocytes but are negative for surface Ig (Leceta & Zapata 1991). Furthermore, the cellularity of the PALS is substantially reduced upon adult thymectomy or treatment with antithymocyte antiserum (Pitchappan & Muthukkaruppan 1977), and a less pronounced loss in cellularity is observed after adult thymic involution (Borysenko & Cooper 1972). As such, the reptilian PALS seems more similar to the mammalian WP.…”

Section: Reptilesmentioning

confidence: 99%

Emergence and Evolution of Secondary Lymphoid Organs

Neely

Flajnik

2016

Annu. Rev. Cell Dev. Biol.

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For effective adaptive immunity to foreign antigens (Ag), secondary lymphoid organs (SLO) provide the confined environment in which Ag-restricted lymphocytes, with very low precursor frequencies, interact with Ag on Ag-presenting cells (APC). The spleen is the primordial SLO, arising in conjunction with adaptive immunity in early jawed vertebrates. The spleen, especially the spleen’s lymphoid compartment, the white pulp (WP), has undergone numerous modifications over evolutionary time. We describe the progressive advancement of splenic WP complexity, which evolved in parallel with the increasing functionality of adaptive immunity. The Ag-presenting function of follicular dendritic cells (FDC) also likely emerged at the inception of adaptive immunity, and we propose that a single type of hematopoietically derived APC displayed Ag to both T and B cells. A dedicated FDC, derived from a vascular precursor, is a recent evolutionary innovation that likely permitted the robust affinity maturation found in mammals.

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Section: Reptilesmentioning

confidence: 99%

Emergence and Evolution of Secondary Lymphoid Organs

Neely

Flajnik

2016

Annu. Rev. Cell Dev. Biol.

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“…The thymus, the primary lymphoid organ for T cell development in jawed vertebrates, undergoes involution seasonally in some reptiles, resulting in variations in the splenic microarchitecture ( 66 , 67 ). Thymectomy ( 68 ) and adult thymic involution ( 69 ) also result in reduced cellularity of the PALS region of the reptilian spleen, further evidence that this region is an organized T cell zone. While reptiles have organized B and T cell zones, they do not form observable GCs in their white pulp ( 63 , 64 ).…”

Section: Reptiles: Pals and Pels Are Not Enough (For Robust Affinity ...mentioning

confidence: 88%

450 million years in the making: mapping the evolutionary foundations of germinal centers

Matz

Dooley

2023

Front. Immunol.

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Germinal centers (GCs) are distinct microanatomical structures that form in the secondary lymphoid organs of endothermic vertebrates (i.e., mammals and some birds). Within GCs, B cells undergo a Darwinian selection process to identify clones which can respond to pathogen insult as well as affinity mature the B cell repertoire. The GC response ultimately generates memory B cells and bone marrow plasma cells which facilitate humoral immunological memory, the basis for successful vaccination programs. GCs have not been observed in the secondary lymphoid organs of ectothermic jawed vertebrates (i.e., fishes, reptiles, and amphibians). However, abundant research over the past decades has indicated these organisms can produce antigen specific B cell responses and some degree of affinity maturation. This review examines data demonstrating that the fundamentals of B cell selection may be more conserved across vertebrate phylogeny than previously anticipated. Further, research in both conventional mammalian model systems and comparative models raises the question of what evolutionary benefit GCs provide endotherms if they are seemingly unnecessary for generating the basic functional components of jawed vertebrate humoral adaptive immune responses.

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“…The spleen, on the other hand, is a major peripheral lymphoid organ containing a large number of lymphocytes that are separated morphologically into T-and B-lymphocyte populations. In the lizard Calotes versicolor, adult thymectomy results in severe depletion of the white pulp of the spleen; although specific reference to T-and B-lymphocyte specific areas was not made (Pitchappan and Muthukkaruppan, 1977). T-lymphocytes reside primarily in the lymphocyte sheaths and B-lymphocytes comprise most of the Malpighian bodies.…”

Section: Discussionmentioning

confidence: 99%

Altered histology of the thymus and spleen in contaminant‐exposed juvenile American alligators

Rooney

Bermudez

Guillette

2003

Journal of Morphology

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Morphological differences in spleen and thymus are closely related to functional immune differences. Hormonal regulation of the immune system has been demonstrated in reptilian splenic and thymic tissue. Spleens and thymus were obtained from juvenile alligators at two reference sites in Florida, USA: Orange Lake and a National Wildlife Refuge, Lake Woodruff, as well as from a contaminated lake, Lake Apopka. Lake Apopka has been extensively polluted with agricultural pesticides. Tissues were prepared for histological analysis to determine if previously detected endocrine abnormalities associated with contaminant exposure might also be reflected in morphological differences in splenic and thymic structures important for immunological response. Similar tissues were taken from captive-raised juvenile female alligators (3 years old) that were hatched from eggs collected on Lake Woodruff and Lake Apopka. Differences in thymic ratios (medulla/cortex) were found among alligators collected from the two lakes (P = 0.0051). Alligators from Lake Apopka had smaller thymic ratios than animals from either reference lake. Males from Lake Woodruff had significantly smaller lymphocyte sheaths in the spleen than females (P = 0.0009), indicative of a normal sexual dimorphism. Lymphocyte sheath width differed among females obtained from the three lakes, with females from Lake Apopka having the smallest sheath width and those from Orange Lake having the largest. Malpighian body area was largest in alligators from Orange Lake, intermediate in Lake Woodruff, and smallest in Lake Apopka. In contrast to that observed for wild-caught animals, no difference was found in the thymic medulla/cortex ratio of captive-raised female alligators (P = 0.378). Captive-raised female alligators from Lake Apopka and Lake Woodruff displayed lake-associated differences in lymphocyte sheath width as observed in wild animals; Lake Apopka alligators had smaller lymphocyte sheath width compared to Woodruff alligators (P = 0.0396). In contrast to wild-caught animals, area of the Malpighian bodies did not differ by lake in the captive-raised female alligators (P = 0.066). The enlarged thymic cortex suggests a change in T-lymphocyte maturation within the thymus of alligators from a contaminated environment, Lake Apopka. The results point to alterations in the histology of the thymus and spleen. Further studies are required to examine the functional significance of these observations.

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Thymus‐dependent lymphoid regions in the spleen of the lizard, Calotes versicolor

Cited by 17 publications

References 20 publications

Emergence and Evolution of Secondary Lymphoid Organs

Emergence and Evolution of Secondary Lymphoid Organs

450 million years in the making: mapping the evolutionary foundations of germinal centers

Altered histology of the thymus and spleen in contaminant‐exposed juvenile American alligators

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