The Incidence of Follicular Structures in the Human Thymus at Autopsy

Abstract

Summary.A survey of 928 ;iiifopsy ihymie glands from hospital and accident deatlis was carried init lo dcterdiine the incidence of follicular structures in the human tliyinic incdulla. It was foiintl that, contrary to previous opinions, follicLilar structures with pale centres are indeed common in the norinal human tliyuius. The incidence in youn^ people is identical with the figure quoted for myasthenia gravis. Follicles tire not present in nconatcs and the incidence decreases with illness and with advancing age.

The prevalence of human thymic lymphoid follicles is lower in suicides

“…The antigen(s) involved can be 'non-self' and a component of a normal immune response or 'self' and a component of an autoimmune process. The findings serve to reinforce the previously indicated need for caution in attaching pathological significance to the mere presence of lymphoid follicles in the human thymus [14,15,28] and in the use of the term thymic hyperplasia [13] if any follicles are discovered in sections of a thymus.…”

“…Previous studies have found a lower prevalence of thymic lymphoid follicles in subjects dying after some time in hospital than is found in [14,24]. These studies suggested that this decreased prevalence is a stress effect and that the stress has to be present for some days.…”

“…Information about the effects of stress on the morphology of the human thymus has been limited to that gained from autopsy studies. These have shown a decreased volume of the thymic cortex [9] associated with an increased level of apoptosis (termed pyknosis in early studies) of cortical lymphocytes [2,8,16] and decreased prevalence of thymic (B) lymphoid follicles [14,24] consequent on the stress of organic illness or injury.…”

Phenotypic and functional analysis of lymphocytes in myasthenia gravis

“…Indeed, prominent intrathymic germinal center formation has been described in only two other clinical settings, e.g., SLE [15,73] and thyrotoxicosis [107]. Smaller and less numerous follicles may be present in thymus glands of healthy individuals [77,126]. Germinal center formation in peripheral lymph nodes occurs in response to the local trapping of antigen.…”

Comparison of thymic histology with response to thymectomy in myasthenia gravis

“…Firstly, the presence of lymphoid follicles in human thymus which Mackay et al (1968) term 'thymitis' is not specific for myasthenia gravis. Lymphoid follicles are readily detectable in many young subjects who die suddenly (Middleton, 1967), or who have operations to correct congenital heart disease (Henry, 1968;Vetters and Barclay, 1973). Further, lymphoid follicles are seen frequently in other diseases now believed to have an autoimmune basis-indeed, Sloan (1943) observed lymphoid follicle formation in subjects with Addison's disease, acromegaly, and thyrotoxicosis.…”