CD2/CD21 index: A new marker to evaluate udder health in dairy cows

Abstract

Lymphocytes play a significant role in the immunological processes of the bovine mammary gland and were found to be the dominant cell population in the milk of healthy udder quarters. The objective of this study was to investigate the quantitative relationship between CD2 + T and CD21 + B lymphocytes using flow cytometry. In a first study, quarter foremilk samples from apparently healthy udder quarters [somatic cell counts (SCC) ≤100,000 cells/mL; n = 65] were analyzed and compared with diseased quarters (SCC >100,000 cells/mL; n = 15). Percentages of CD2 + T cells were significantly higher in milk samples with SCC ≤100,000 cells/mL than in those with SCC >100,000 cells/mL, whereas percentages of CD21 + B cells developed in the opposite direction. As a result of this opposing trend, a new variable, the CD2/CD21 index-representing the percentages of CD2 + cells per CD21 + cells-was defined. Although diseased quarters with SCC >100,000 cells/mL and the detection of major pathogens revealed generally CD2/CD21 indices <10, values >10 were observed in apparently healthy quarters. Hence, a CD2/ CD21 index cutoff value of 10 may be suitable to aid differentiation between unsuspicious and microbiologically suspicious or diseased udder quarters. To test whether CD2/CD21 indices <10 were primarily related to pathogens, quarters with SCC ≤100,000 cells/mL and >100,000 cells/mL with different bacteriological status (culture negative, or minor or major pathogens) were selectively examined in a second biphasic study. In the first trial, 63 udder quarters were analyzed and 55 of these quarters were able to be sampled again in the second trial carried out 14 d later. In both trials, results of the first study were confirmed. Indeed, CD2/ CD21 indices <10 were also found in quarters showing SCC ≤100,000 cells/mL and containing minor or major pathogens at the time of the current or previous bacteriological analysis. The results of our examinations indicated a clear relationship between the CD2/CD21 index and the bacteriological status of the mammary gland. In combination with SCC, it offers a new marker for quick differentiation of unsuspicious and microbiologically suspicious or diseased udder quarters.

Flow cytometric analysis: Interdependence of healthy and infected udder quarters

“…Although the study size is limited, our data support the hypothesis of interdependence of quarters based on the influence of the udder infection on the percentage of B cells in uninfected quarters. Here, a higher percentage of CD21 + cells was found in infected quarters (15.92 ± 1.84%; n = 6), as previously reported by Schwarz et al (2013) and Riollet et al (2001), which may explain the increased percentage of B cells in the neighboring quarters encountered here. This finding may be related to local lymphocyte proliferation (Concha et al, 1996) and the development of a humoral response (Riollet et al, 2001).A higher percentage of T cells (CD3 + ) was observed in infected quarters (13.64 ± 5.35%; n = 6), as previously described by Rivas et al (2002) after challenge with S. aureus.…”

“…It is known that CD21 + cells are increased in milk samples with high SCC, whereas the proportions of CD2 + and CD3 + cells are decreased (Rivas et al, 2007;Schwarz et al, 2013). The CD2 + /CD21 + index has recently been proposed as a new marker for the rapid differentiation of normal versus diseased udder quar-ters (Schwarz et al, 2013).…”

“…It is known that CD21 + cells are increased in milk samples with high SCC, whereas the proportions of CD2 + and CD3 + cells are decreased (Rivas et al, 2007;Schwarz et al, 2013). The CD2 + /CD21 + index has recently been proposed as a new marker for the rapid differentiation of normal versus diseased udder quar-ters (Schwarz et al, 2013). Regarding our findings, the increase in the proportion of CD21 + cells in uninfected quarters from infected udders may affect the predictive value of the CD2 + /CD21 + index for diagnosing IMI and therefore requires further investigation.…”

Bovine Mastitis: Frontiers in Immunogenetics

“…Mammary epithelial cells are known to play a role in early responses through the production of cytokines like IL-8 and other factors with antimicrobial activities ( 28 , 29 ). If the bacteria survive these innate host defenses, adaptive immune responses mediated by T and B cells are required to clear the infection ( 30 ). The ideal immune response being one that appropriately recognizes epitopes on the invading pathogen to initiate swift and accurate clearance mechanisms while maintaining minimal pathological consequences.…”

Role of the JAK-STAT Pathway in Bovine Mastitis and Milk Production

“…However, in the early phase of infectivity, the neutrophil and inflammatory cytokine levels increase quicker than milk SCCs [88]. That is why, nowadays, more interest is paid to the increase in cells and cytokine levels in milk and blood, respectively, rather than just the overall SCC, which may provide an early status of udder health [89]. A study showed that inflammatory cytokines (IL-6, IL-17, and IFN-γ, TNF-α) could be used as subclinical mastitis indicators, in addition to SCSs and SCCs [51,86,90].…”