Our previous studies showed that some antigenic and mitogenic substances, when locally injected into mice, efficiently produced new lymph follicles outside pre-existing follicles in draining lymph nodes, whereas others had virtually no effect. In the present experiments, young adult male mice were injected with several antigens and mitogens in the rear footpad, and the number and development sites of newly produced lymph follicles in the draining popliteal nodes were studied using serial sections of the nodes obtained between 5 and 21 days after injection. In the unstimulated state, each popliteal node contained a limited number of lymph follicles which mostly lay in a portion of the peripheral cortex overlaying the deep cortex (this portion is referred to as the PCOU), whereas a portion of the peripheral cortex extending beyond the deep cortex (referred to as the PCBU) was underdeveloped with only occasional follicles. Mice treated with soluble PHA or fluid tetanus toxoid developed germinal centers in association with existing follicles but failed to produce new follicles. The PCBU of the draining nodes remained underdeveloped, and the number and distribution pattern of lymph follicles within a draining node were comparable to those in the control node. Animals treated with LPS (50 micrograms), Con A, alum-precipitated PHA or alum-precipitated tetanus toxoid produced significantly large numbers of new follicles outside pre-existing follicles in the draining nodes, the new follicles produced in the PCBU being generally more numerous than those in the PCOU. In these draining nodes, the peripheral cortex, comprising a number of follicles, was found to overlie the deep cortex and extend beyond the deep cortex towards the hilar region. In animals given a less effective stimulant, such as ferritin or a smaller dose of LPS (10 micrograms), the draining nodes produced a relatively small number of new follicles, most of which were formed in the PCBU. The present results indicate that in the mouse popliteal node, the PCBU is morphologically underdeveloped under normal conditions, but develops lymph follicles in response to exogenous stimuli more readily than the PCOU, and that substances efficient in inducing follicle formation can be regarded as capable of stimulating the development of the peripheral cortex.
We reported previously that surgical interruption of the afferent lymphatics to the popliteal node at the lowest edge of the popliteal fossa in young rats caused suppression of ontogenic development of the popliteal node. However, in that experiment we did not take into consideration the fact that, in the rat, the popliteal node sometimes receives minute afferent lymphatic channel(s) from the tail. In the present study, therefore, we interrupted the afferent lymphatic vessels at the lowest edge of the left popliteal fossa in Wistar rats at 7 days after birth in order to examine the effects of lymphatic drainage from the tail on the treated nodes, and sacrificed the animals at 2, 5, 10 and 18 weeks after the operation. A solution of 0.4% Evans blue was injected into the root of the tail on the left side 30 min before the animals were killed. Treated nodes receiving lymphatic channel(s) from the tail were stained with the dye and referred to as Eb(+)-treated nodes, whereas those without the channel(s) were unstained and referred to as Eb(-). At 7 days after birth, the normally developing popliteal node weighed 0.2 mg, and its parenchyma was composed of reticular cells with dispersed lymphoid cells. At 4 weeks after birth, each normal node weighed 2-3 mg; its parenchyma was comprised of two layers, an outer layer of peripheral cortex containing 30-40 lymph follicles and an inner discontinuous layer of deep cortex made up to 2-3 deep cortical units.(ABSTRACT TRUNCATED AT 250 WORDS)
The histologic localization of fibronectin (FN) in normal human skin, granulation tissue, hypertrophic scar, mature scar, progressive systemic sclerotic skin, and tissue of other fibrotic disorders was investigated by an indirect immunofluorescence technique using specific antiserum prepared in rabbits against purified human plasma FN. In granulation tissue that developed just after traumatic wounding, FN seemed to increase remarkably in the wound as a fibrillar network. In the hypertrophic scar, one to five years after wounding, FN was detected in a linear or curling arrangement throughout the dermis. On the contrary, FN gradually decreased in the wound of the mature scar five to 20 years after wounding. There were some interesting observations among other diseases. In the skin of patients with progressive systemic sclerosis and morphea, FN was found to be localized faintly on the dermoepidermal junction and papillary dermis. In the involved skin of dermatofibroma, FN was observed in a curling arrangement throughout the dermis.
The timing of the first appearance of lymph follicles and germinal centres in various lymph nodes, and the ways in which numbers of these and IgM‐synthesising cells increase within the nodes, were investigated in male and female C57Bl/6N mice aged from 4 d to 16 wk. The lymphoid organs examined were the Peyer's patches, spleen, somatic (submandibular, deep cervical, brachial, axillary, inguinal and popliteal) and visceral (mesenteric and lumbar) lymph nodes. Primary follicles appeared in most somatic lymph nodes 6 d after birth. The number of follicles per node then increased rather sharply in larger lymph nodes and slowly in smaller nodes, up to 28 d of age, reaching a level which varied according to the location of the node. Thereafter, the number of follicles in the somatic lymph nodes increased only slightly to moderately, reaching a peak or plateau at 8–12 wk. In the mesenteric (ileocaecal) nodes, primary follicles first appeared at 12 d, then increased linearly during the suckling period and after weaning to reach a plateau at 8 wk of age. Germinal centres appeared in the submandibular and mesenteric nodes at 28 d and their numbers increased consistently in the latter, while remaining low in the former. The impact of possible ‘natural’ exogenous antigen stimulation of the various lymph nodes was estimated from the presence of IgM‐synthesising cells and germinal centres. Differences between the patterns of age‐dependent changes in the numbers of lymph follicles observed in the somatic and mesenteric lymph nodes during their ontogeny are discussed in relation to differences in the magnitude of the exogenous antigen stimulatory effect. We also found that the variations in the numbers of lymph follicles produced in somatic lymph nodes at different locations during the first 28 d after birth reflected differences in the dimensions of the body regions drained by a particular somatic lymph node at this stage of development.
Lymphatic vessels afferent to the popliteal nodes in young adult rats and guinea pigs were interrupted at the lowest edge of the popliteal fossa, and regressive changes in the nodes occurring 4 to 16 or 18 weeks after surgery were re-examined histologically. In the rat, some popliteal nodes were drained by lymphatic channel(s) from the tail. After surgery, the popliteal nodes without lymphatic channel(s) from the tail underwent regression of all their constituent deep cortical units and also the peripheral cortex comprising lymph follicles, until at 18 weeks, the lymphoid organization of the node reached a minimal level. On the other hand, in popliteal nodes having a lymphatic channel from the tail, some deep cortical units and the overlying peripheral cortex underwent hypotrophy, leaving the remaining units and their overlying peripheral cortex little affected. In the guinea pig, the treated nodes underwent progressive atrophy and ultimately became rudimentary, or even vanished, after 16 weeks. Treated rudimentary nodes were composed largely of stromal cells only, and these were replaced to a various extent by fat. The present results are discussed in relation to complete and incomplete inhibition of the afferent lymph flowing into the surgically treated nodes.
The effect of blockage of the afferent lymphatic vessels on the development of popliteal lymph nodes in the rat was studied. The afferent lymphatic vessels to each popliteal node were surgically interrupted at the lowest edge of the popliteal fossa at 3, 7 or 28 days after birth and the popliteal nodes were obtained from treated animals at 4, 8 or 16 weeks after the operation. At 7 days after birth, each popliteal node was small and weighed 0.2 mg. Its parenchyma consisted of reticular cells and a small number of dispersed lymphoid elements. Four weeks after birth, each node weighed 4-5 mg, and its parenchyma comprised two layers, an outer continuous layer of peripheral cortex containing 40-50 lymph follicles and an inner discontinuous layer of deep cortex made up of 4-5 deep cortical units. At 10-12 weeks after birth, each node weighed about 10 mg and showed full structural development; the peripheral cortex contained 100-130 lymph follicles and the deep cortex consisted of 4-6 well developed units. The popliteal node was drained by 4-6 afferent lymphatic vessels, which opened into the subcapsular sinus of the node. Each lymphatic opening was topographically associated with a respective deep cortical unit, as previously described by Bélisle and Sainte-Marie (1982). In animals treated at 3 or 7 days after birth, the development of the popliteal nodes was considerably inhibited. Four weeks after surgery, each node showed 10-30 lymph follicles in the peripheral cortex and 1-3 small units in the deep cortex. Sixteen weeks after surgery, the node weighed about 4 mg and its cortex exhibited about 50 lymph follicles in the peripheral cortex and only 2 units in the deep cortex. The popliteal nodes of the treated animals generally received 2 afferent lymphatic vessels. In animals treated at 4 weeks after birth, the popliteal nodes showed no gain in weight for following 16 weeks. Four weeks after surgery, each node usually had 4-5 deep cortical units and 50-60 lymph follicles. Thereafter, some units and their overlaying peripheral cortex underwent atrophy, while others persisted. Sixteen weeks after surgery, the popliteal node showed only 2 deep cortical units and 50-60 lymph follicles, and was drained by 2 afferent lymphatic vessels. Surgical interruption of the afferent lymphatic vessels to the popliteal node at the lowest edge of the popliteal fossa did not obliterate all the draining lymphatic vessels , but reduced the number of vessels opening into the node.(ABSTRACT TRUNCATED AT 400 WORDS)
