Morphometric analysis of small intestinal mucosa. II. Determination of lamina propria volumes; plasma cell and neutrophil populations within control and coeliac disease mucosae.

Morphometric techniques were employed to measure (i) lamina propria volumes and (ii) the absolute numbers of neutrophils and plasma cells, of A, M and G isotype, within the lamina propria of jejunal mucosa. Mucosal specimens were obtained with a Watson capsule (a) from 5 patients with untreated coeliac disease, and again at least 3 months after starting on a gluten-free diet, and (b) from 9 control individuals. Lamina propria volume of untreated coeliac mucosa (2.5 +/- 0.17 X 10(6) micron3 ) was increased 2.3-fold (p less than 0.01) above that of control mucosae (1.35 +/- 0.08 X 10(6) micron3 ). Compared with control mucosae, there was a 20-fold increase of neutrophils in untreated coeliac mucosae (p less than 0.005). The total complement of all plasma cells in untreated coeliac mucosae (309) was twice that (149) of control mucosae. The populations of each isotype were also significantly increased over controls by factors of 1.6 (IgA; p less than 0.05), 3.0 (IgM; p less than 0.01) and 3.5 (IgG; p less than 0.01). Their percentage distributions in untreated coeliac mucosae (A:M:G--52:43:5) differed from those in control mucosae (A:M:G--69:28:3) but were restored after treatment with a gluten-free diet. However, when each isotype was expressed per unit volume of lamina propria, there was an apparent fall (X 1.4) in IgA cells, while the increase in IgM and IgG cells was less marked i.e. X 1.4 and X 1.5 respectively. These precise measurements explain why many previous investigators found a paradoxical fall in IgA cells because the (increased) volume of distribution of these cells was not taken into account. The importance of morphometric techniques in achieving valid cell 'counts' within the intestinal mucosa is thus illustrated by this study.