Studies on the immunity of sheep to Oesophagostomum columbianum: Proteins and haemagglutinatiog antibodies in mucous exudates and intestinal tissue extracts

Abstract

A passive haemagglutination test utilizing formalinized, tanned, sensitized sheep erythrocytes was developed in order to study the antibody content of serum, mucus, and tissue extracts from sheep infested with Oesophagostomum columbianum. This test was compared with similar techniques developed by other workers for different helminth-host systems and was found to be more sensitive. The cells also retained their sensitivity as an antigenic suspension for a number of days.

The haemagglutinating antibody titre of the serum was found to be consistently low: 1 : 3.3 in non-infested controls, 1 : 30 after a first, and 1 : 45.3 after a second infestation.

Three extracts were made for each of nine separate sections of the alimentary tract: two 10 ft lengths of the small intestine anterior to the ileocaecal valve, one 2 ft length of the caecum and large colon, and six equal lengths of the colon through to the anus. These three extracts comprised a mucous exudate in saline, a saline homogenate of the mucosa, and a similar homogenate of the muscularis mucosae.

The antibody titre of the mucous exudate was low in the controls but very high in the animals with first and second infestations compared with the titre obtained for the serum. The antibody titre was also much greater after first than after second infestation. This was attributed to the adult worm irritating the mucosa and stimulating the release of antibody; no adult worms were found after second infestation. The very low antibody titre of the serum relative to that of the mucous extract may be related to a. localized site of production within the mucosa of the gut. There was also a correlation between the site of infestation by the adult in the large lcolon and proximal colon, and the peak titre of the haemagglutinating antibody. This peak was also related to a peak in the relative concentration of ß and y-globulins in the mucus after first infestation and in the y -globulins after second infestation.

The mucosal extracts were much richer in haemagglutinating antibody than either of the other two samples. Again the antibody titre was highest within the area infested by the adult worms, and there was a similar distribution of ß and y-globulins throughout this area as for the mucous exudate.

The final extract tested was from the tunica muscularis. These exudates gave the lowest antibody titres of the three samples; this was related to the paucity of lymphoid tissue in the muscle layers.