It is important to clarify if the lymphoid aggregates occur infiltrrating exocrine or endocrine parts or in the connetive tissue surrounding the organ or invade it through connective tissue trabeculae. In this last case, it could be just a reflect of the presence of  lymphocytes in any loose coonective tissue (it depends on the amount of cells). Otherwise, it could be an autoimmune condition as occurs in the thyroid of Obeses chicken

Dear Miguel matos..

Its not normal to finds aggregation of lymphoid cells in the pancreas of chickens. But in some case (non pathological case ) I was found aggregation of lymphoid cell in pancreas in case of vaccine administration against ND " new castle disease" through drinking water ... 

great regards 

It depends on numbers,distribution and exposure to antigenic stimulation. In birds, a few,  small non-follicular aggregates of lymphoid tissue may occur in  many organs and tissues and this should not be regarded as inflammation. However when the numbers are increased one should considered the possibility of exposure to Avian encephalitis virus. In young birds which survive infection with Avian encephalomyelitis virus, multiple dense aggregates of lymphocytes, in diffuse of folicular patterns may be found in pancreas and also in several other organs including heart, proventriculus and gizzard wall  which are considered pathognomonic for this disease.

Dear Miguel,

I also agree with both opinions. Providing a couple of pictures might be helpful

Cheers,

Ivan

It is important to clarify if the lymphoid aggregates occur infiltrrating exocrine or endocrine parts or in the connetive tissue surrounding the organ or invade it through connective tissue trabeculae. In this last case, it could be just a reflect of the presence of  lymphocytes in any loose coonective tissue (it depends on the amount of cells). Otherwise, it could be an autoimmune condition as occurs in the thyroid of Obeses chicken

Here I have 3 images, from 3 different healthy birds and I found these infiltrates. They are the only ones present in the whole histological slide. 

Have you some images at higher magnifications?

Hi Miguel This is very interesting - thanks for the pictures. If this is the only feature of note in otherwise healthy birds and there is no other pathology in  tissues elsewhere, then this could be interpreted as an incidental finding. The lymphocyte aggegates appear to be more of a perivascular distribution and being the only ones on the histo slide, I perhaps would suggest this is perhaps related to non-specific antigenic stimulation - the use of vaccines (see Vael's comment above) could be well related - how old are these birds? have they been subjected to standard vaccination or are these experimental birds? I have no experience on autoimune conditions in poultry commercial production so i can not offer any comments at this respect. I hope this helps.

There are many Abs specific to chicken T and B lymphocytes try to characterize the populations of the aggregates

Here, I added to magnifications!

Cristina Garcia - Rueda, they are 4, 14 and 21 days old respectively. They are experimental birds.

Many thanks!

Thank you for the new pictures It is difficult to ensure the significance of these infiltrations without a more detailed phenotypical analysis; they resemble, in some aspects, to lymphoid nodules occurring in the thyroid of chickens suffering Hashimoto disease (Obese chickens) but, I agree with Cristina, that they are restricted just to connective tissue trabeculae without invading exocrine tissue and they could be therefore normal infiltrates as well

Thank you all for sharing your knowledge. I went deeply into literature and I found some studies from the 40's/50's on lymphoid tissue in the Pancreas of Chickens. It appears that circumscribed lymphocytic follicles are normal. Apparently birds possess numerous widely scattered acumulations of lymphoid tissues in various organs. It is said that they correspond to the lymph nodes of mammals.

http://www.ncbi.nlm.nih.gov/pubmed/15406727

http://www.ncbi.nlm.nih.gov/pubmed/15399222