SummaryThe segregation of 11 well‐defined SLA haplotypes was investigated in 40 Land‐race and 48 Large White Danish and Swiss litters. Among the 11 haplotypes, the segregation of one (SLA 20–8.2.11) deviated significantly from the expected 1: 1 segregation ratio in back‐cross families. Tests indicated that these families were homogeneous with respect to segregation distortion, although the distortion was more pronounced in litters sired by heterozygous Danish boars than by heterozygous Swiss boars and Danish and Swiss sows. The data presented do not allow any definite conclusion about the cause of the segregation distortion. The possibility of the distortion being caused either by a complex similar to the T/t‐complex found in mouse and contemplated in man or directly by the SLA region is discussed.

SummaryAlloantisera were produced in common Swiss and Danish swine breeds by immunization with leucocytes or skin‐grafts. Out of the 126 antisera, 66 were chosen for further study based on titrations employing lymphocytes from unrelated pigs typed with French SLA antisera (Vaiman, Chardon & Renard, 1979). The 66 selected antisera and the French reagents defining 26 SLA specificities were used to type lymphocytes from 595 unrelated pigs of the common Swiss and Danish breeds. The reaction‐patterns of the French, Swiss and Danish antisera were adequately correlated for the French SLA specificities Nos FJ 2, 3, 6, 7, 8, 9, 11, 14, 19, 20 and 24 and for the haplotypes FJ 15.1.18 and FJ 5.4. In addition, a cluster of correlated Danish and Swiss antisera characterized a new specificity, provisionally designated CPH 31. This specificity was frequent in the Danish Landrace pigs.Using the reagents identified in this report, the segregation of SLA markers was studied. Back‐cross families demonstrated segregation of 15 distinct SLA haplotypes of which 14 are common in French Landrace or Large White. Differences were found in haplotype frequencies in both the Swiss and the Danish Landrace and Large White breeds.

Since the first description of blood group chimerism in cattle (Owen, 1945) this subject has been a continual source of interest for studies in domestic animals. The literature describing this rare occurrence in pigs is summarized in Table 1. In the present paper we describe results obtained by examination of blood groups, red cell enzymes, histocompatibility (SLA) antigens and karyotypes in a Landrace pig, which probably establish the first example in pigs of chimerism involving two SLA cell populations.During the blood grouping of samples from pig progeny testing stations, atypical reactions were observed in a sample from a male pig No 241 (2 months of age) by using the Ka, Kc, Kb, Mb and Ee reagents. Subsequently, differential haemolysis proved the presence of two distinct red cell populations. Following treatment of red cells with anti-Ka, 39 % of the cells were left intact, while after treatment with anti-Kb, 61 % of the cells remained unaffected. As can be seen from Table 2, typing of the two cell fractions revealed differences in four blood group systems as well as the Pgd and Ada enzyme systems. Neither of the two cell fractions possessed types identical to those observed in the siblings. A more thorough examination of the siblings using absorption tests which are able to disclose 1 % cell fractions did not show any sign of red cell mixtures. The proportion of the red cell fractions in pig No 241 remained unchanged during the study. According to the standard procedures of progeny testing stations, No 241 was slaughtered at 90 kg ( 5 months of age) and further tests were excluded.SLA typing was performed on lymphocytes from the apparent chimeric pig (No 241), the parents and two littermates. The class I SLA antigens were determined with the panel of SLA antisera described by Kristensen et al. (1985) using the micro-lymphocytotoxicity test. Four distinct SLA haplotypes were demonstrated on the lymphocytes from the chimeric pig, namely FJ 20-8.2.11, FJ 20-7.2, FJ 10.14 235

A new, non-MHC cell membrane leucocyte alloantigen was detected in pigs by the complement dependent lymphocytotoxic technique. The new leucocyte system was designated SLD. Its product antigen SLD-1 was demonstrated to segregate independently of the SLA, SLB, SLC, A and E antigens. Family studies supplied evidence of a dominant inheritance of SLD-l. Since an allelic antigen could not be demonstrated, only two alleles for this locus are reported, namely SLDl and SLD-. No evidence of linkage was detected between the above mentioned leucocyte alloantigenic systems and SLD. The antigen was detected on enriched suspensions of T and B cells from peripheral blood, but it was not detected on erythrocytes, granulocytes and thrombocytes.